As the NET translators point out:
There are several options for the meaning of Jesus’ reply Leave the
dead to bury their own dead:
- Recent research suggests that burial customs in the vicinity of Jerusalem from about 20 B.C. to A.D. 70 involved a reinterment of the
bones a year after the initial burial, once the flesh had rotted away.
At that point the son would have placed his father’s bones in a
special box known as an ossuary to be set into the wall of the tomb.
Thus Jesus could well be rebuking the man for wanting to wait around
for as much as a year before making a commitment to follow him. In 1st
century Jewish culture, to have followed Jesus rather than burying
one’s father would have seriously dishonored one’s father (cf. Tobit
4:3-4).
- The remark is an idiom (possibly a proverbial saying) that means, “The matter in question is not the real issue,” in which case Jesus
was making a wordplay on the wording of the man’s (literal) request
(see L&N 33.137).
- This remark could be a figurative reference to various kinds of people, meaning, “Let the spiritually dead bury the dead.”
- It could also be literal and designed to shock the hearer by the surprise of the contrast. Whichever option is preferred, it is clear
that the most important priority is to follow Jesus.
I will explore these four options in a little more depth (and some sub-options as well as alternate perspectives). I believe that some overlap occurs in these perspectives and thus someone could believe that more than one option is explanatory simultaneously.
It should also be borne in mind that this occurs in the larger context of Jesus challenging the concept and identity of family and allegiance to national ties vs. the kingdom of God. N.T. Wright elaborates extensively on this in Jesus and the Victory of God (1996), saying,
"...the only explanation for Jesus' astonishing command is that he
envisaged loyalty to himself and his kingdom-movement as creating an
alternative family (p. 401)."
I will not elaborate further on this position as it moves beyond the text into the realm of doctrinal application, but it should be noted as a likely backdrop for Matthew's record of this encounter with the disciple.
Option 1: Rejection of Secondary Burial Practices
In first-century Jewish Palestine, the son would commonly bury his father on the day of his passing. The family would then mourn for one week (a practice referred to as 'sitting shivah'). After the flesh had decayed from the bones (approximately one year later), the son would stop mourning and place the father's bones in an ossuary (this was sometimes called a "second burial" or "ossilegium"). Keep in mind that families had shared tombs for the entire family during this time period (Meyers, Eric M. "Jewish Ossuraries: Reburial and Rebirth: Secondary Burials in Their Ancient Near Eastern Setting," Biblica et Orientalia. Rome: Biblical Institute Press, 1971).
The Jewish Virtual Library refers to this practice of using ossuaries for secondary interment:
Small stone chests, used for the secondary interment of human bones,
were extremely popular among the Jewish population during the Second
Temple period, i.e., between c. 40 B.C.E. and 135 C.E.. Ossuaries
found by Hachlili at Jericho are dated to a more restricted time
period: 10–68 C.E. They are mainly known from tombs in the vicinity of
Jerusalem, but examples are known from Galilee (e.g., Nazareth), the
Shephelah (e.g., Modi'in), and the lower Jordan River region (e.g.,
Jericho). A typical ossuary had a length of about 2.5 ft., so that it
might accommodate the long bone of an adult leg, which is the longest
bone in a human body. The ossuaries taper slightly toward the bottom;
some stand on four low legs; they are made of soft limestone with flat
or vaulted lids. Many contain scratched inscriptions on their sides in
cursive Hebrew, Aramaic, or Greek, or in two languages (a few
inscriptions were made with charcoal).
Jesus may have merely been opposing this practice that would have required an additional year of mourning and family obligation after the first burial. This option takes into account both internal and external evidence (the disciple does not make an excuse to not follow Jesus, but rather asks for time before doing so; and this makes sense in light of the above-mentioned cultural practices). There are a variety of reasons why he may have opposed the practice, one of which deserves special mention.
Jesus May Have Opposed Purification Beliefs Associated with Ossilegium
This is more of a speculative subset of option one which hypothesizes beyond the option as presented by the NET translators. Associated with the practice of ossilegium ("second burial") in first-century Judaism was the concept that the practice played some role in the purification of the deceased party's soul.
Ossilegium was an important family event and a religious act. The Jews
believed in life after death and resurrection. The decomposition of
the flesh thus purified the deceased’s soul, a necessity for
resurrection (University of Missouri, Introduction to exhibit
"Atonement for the Afterlife: The Jewish Practice of Ossilegium,"
Museum of Art and Archaeology, 2013).
This is disputed and would clearly be confined only to first-century Jewish sects who believed in the resurrection of the dead (such as the Pharisees) and is thus not applicable to all first-century Jews (Fine, Steven. "A Note on Ossuary Burial and the Resurrection of the Dead in First-Century Jerusalem," Journal of Jewish Studies 51, no. 1 (2000): 69-76). However, if it is true, Jesus may have been opposing this specific belief underlying the practice of secondary interment. This position has gained considerable scholarly support in recent years.
Gordon Franz has proposed an interpretation of this statement of Jesus that follows this idea. The entire article is well worth reading and he provides numerous scholarly references to support his argument. Franz concludes,
An amplified (interpretive) rendering of this statement might be:
Look, you have already honored your father by giving him a proper
burial in the family sepulcher. Now, instead of waiting for the flesh
to decompose, this can never atone for sin, go and preach the Kingdom
of God and tell of the only true means of atonement, faith alone in
Christ. Let the bones of your dead father’s ancestors gather his
bones and place them in an ossuary. You follow me! This
interpretation allows for Jesus to have upheld the fifth commandment,
takes the text at face value, and does justice to the Jewish burial
practices of the first century.
Aside from his interpolation of Protestant theology into the mouth of Jesus ("faith alone"), this is a good explanation of the text from this perspective (also note how he deals with the referent of the reflexive possessive pronoun connecting both instances of 'dead' - this stance is not demanded by this approach but is interesting nonetheless).
Option 2: Idiomatic Expression
Jesus may have simply been making a wordplay on the man's statement, idiomatically expressing a sentiment such as:
"You're making excuses. You and I both know this isn't the real
issue."
Possible Racist Motivation
The context provides a possible reason why the disciple did not want to follow Jesus at this specific moment in time: Jesus was about to take his disciples across the Sea of Galilee to the Decapolis city of Gadara (Matthew 8:23; 28). This may have been the first trip Jesus made to minister in Gentile territory. The disciple may have hesitated because he did not want to journey to the "unclean pagan Gentiles."
Aramaism/Hebraism Theory
At the same time, numerous commentators have asserted that the phrase "bury my father" is an Aramaism or Hebraism for "allow me to wait until my father dies so that I can bury him," with the implication that his death is imminent. This option also takes into account both internal and external evidence, and is well supported by numerous scholars (e.g. D.A Carson in Matthew, Mark, Luke, vol. 8 of The Expositor's Bible Commentary, vol. 8, ed. F. Gaebelein, 1984, p. 209). However, it is unclear what (if any) strong textual and linguistic evidence exists for this position, as most who espouse it tend to argue it from the text itself without any references to other texts where this usage appears and it is clear that the father/relative is still alive at the time of writing.
Further Wordplays (A Shout-out to the Aramaic Primacists)
One Aramaic primacist argues that the Aramaic words for 'death' and 'town' are similar and thus a wordplay could be involved expressing:
"Let the town bury their own dead."
While I'm aware that various websites and commentaries assert this, I cannot find any valid and reliable scholarly sources which verify this assertion outside of this minority perspective.
At the same time, it is likely that Jesus was speaking Aramaic, and this is thus a plausible wordplay.
Option 3: Spiritual vs. Physical Death
Options three and four primarily differ on who the referent of the first instance of 'dead' is, as both instances are connected by a reflexive possessive pronoun in the Greek text (virtually everyone agrees that the second instance refers to those who are physically dead, so I have only focused on the dispute over the first instance in this answer). Option three asserts that the spiritually dead should bury the physically dead. Some translators go so far as to interpolate the word 'spiritually' into their translation of this passage in order to express this interpretation:
But Jesus told him, "Follow me now. Let the spiritually dead bury
their own dead" (Matthew 8:22, NLT, emphasis mine; a footnote
indicates that the Greek text does not contain this additional word).
Aside from being a poor translation practice (inserting this word moves beyond translation into the realm of interpretation), the NLT forces option three onto readers (and aside from happening to see the footnote, the reader may not even be aware of alternative interpretations).
This option does not sufficiently deal with the internal evidence (why did the disciple ask for time? It also minimizes the importance of the adverb's primary position in the clause). This option also tends to read later theological perspectives into the text that likely were not intended by Matthew (or Luke for that matter, in his parallel account). However, when combined with option one (rather than taken at face value without the historical context) this becomes a more plausible interpretation.
Option 4: Literal Interpretation
The literal interpretation of Jesus' words is just that: Jesus actually wanted his disciple to disregard his father's burial. This option could be also be combined with some of the other interpretive options.
If combined with (an)other option(s), then each of these combinations would have to be evaluated in light of the strengths of each original option. However, if taken in the literal extreme without combining it with any of the other options, this interpretation shares many of the weaknesses of option three. In addition, this option asserts that Jesus would be commanding this disciple to disobey God's law to honor his parents.
"In Jesus' culture the obligation to bury one's father took precedence
even over saying the Shema" (N.T. Wright, The Challenge of Jesus:
Rediscovering Who Jesus Was & Is, 1999, p. 62).
The main difference of this approach from option three is that it takes the reflexive possessive pronoun to mean that the physically dead should bury the physically dead. In other words, let the bones of the dead that are already in the tomb bury the dead body recently placed in the tomb.
This option could be combined with option one and would have the following meaning: The phrase doesn't make sense, but that is actually the point. Jesus is offering eternal life, yet the disciple would turn to a secondary interment practice to help purify the soul of the deceased so he may live. Jesus would be challenging this notion and thus asserting, if they're alive because of your practice, then let them (the dead relatives) bury your father. No, this is futile. You must follow me for real everlasting life.
Conclusion
There are a variety of plausible approaches to the interpretation of this text. The categories are not all mutually exclusive.