There only seem to be three options I’ve heard or seem possible:
- Adultery (Post-marriage)
- Fornication (Pre-marriage)
- He knew the child was born of the Holy Spirit and want to remove himself from the relationship because he though he was unworthy.
If there are any others please mention and provide verses for them. I've left out rape as it seems inconsistent with the narrative.
Here is the story that seems (to me) to point to Joseph suspecting (or in His mind knowing) Mary had slept with another man.
“Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost. Then Joseph her husband, being a just man, and not willing to make her a publick example, was minded to put her away privily. But while he thought on these things, behold, the angel of the LORD appeared unto him in a dream, saying, Joseph, thou son of David, fear not to take unto thee Mary thy wife: for that which is conceived in her is of the Holy Ghost. And she shall bring forth a son, and thou shalt call his name JESUS: for he shall save his people from their sins. Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying, Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us. Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife: And knew her not till she had brought forth her firstborn son: and he called his name JESUS. - Matthew 1:18-25
However, there doesn’t seem to be a simple way to explain all the details that seem to come up that make this hard to fit into any specific model.
My Notes So Far:
Mary and Joseph were “espoused” or “betrothed” all the way up to Jesus birth. This is important because they were not quite “married” nor “single”. Espousal/Betrothal is a binding covenant prior to the marriage feast and consummation - which is why separate rules are given for it in Deuteronomy 22. Joseph is legally her “husband” and she is is “wife” though they are not yet “married”.
“And in the sixth month the angel Gabriel was sent from God unto a city of Galilee, named Nazareth, To a virgin espoused to a man whose name was Joseph, of the house of David; and the virgin's name was Mary. - Luke 1:26-27
“To be taxed with Mary his espoused wife, being great with child. And so it was, that, while they were there, the days were accomplished that she should be delivered. - Luke 2:5-6
“Then Joseph being raised from sleep did as the angel of the Lord had bidden him, and took unto him his wife: And knew her not till she had brought forth her firstborn son: and he called his name JESUS. - Matthew 1:24-25
People both thought Jesus was legitimately Joseph's son (the statement in John 8:41 is sometimes readinto against this idea, but nothing supports that view)
Is not this the carpenter's son? - Matthew 13:55
And Jesus himself began to be about thirty years of age, being (as was supposed) the son of Joseph, which was the son of Heli, - Luke 3:23
Joseph was a “just man”:
“Then Joseph her husband, being a just man, - Matthew 1:19
Knew his action would make her a publick example (either death or shame)
“Then Joseph her husband, being a just man, and not willing to make her a publick example, was minded to put her away privily. - Matthew 1:19
Worth noting that the “exception” clause for divorce is only mentioned in Matthew where this situation with Joseph thinking about putting away Mary comes up.
But I say unto you, That whosoever shall put away his wife, saving for the cause of fornication - Matthew 5:32
And I say unto you, Whosoever shall put away his wife, except it be for fornication, and shall marry another, committeth adultery: and whoso marrieth her which is put away doth commit adultery. - Matthew 19:9
Divorce only seems legal under fornication:
“The Pharisees also came unto him, tempting him, and saying unto him, Is it lawful for a man to put away his wife for every cause?” - Matthew 19:3 “And I say unto you, Whosoever shall put away his wife, except it be for fornication” - Matthew 19:9
If the “public example” was the death penalty, it seems to require three specific situations.
The death penalty once married (which they were not yet):
“If any man take a wife, and go in unto her, and hate her, And give occasions of speech against her, and bring up an evil name upon her, and say, I took this woman, and when I came to her, I found her not a maid:...” - Deuteronomy 22:13-14 “...if this thing be true, and the tokens of virginity be not found for the damsel: Then they shall bring out the damsel to the door of her father's house, and the men of her city shall stone her with stones that she die: because she hath wrought folly in Israel, to play the whore in her father's house: so shalt thou put evil away from among you. - Deuteronomy 22:20-21
Also death if already married:
“If a man be found lying with a woman married to an husband, then they shall both of them die, both the man that lay with the woman, and the woman: so shalt thou put away evil from Israel. - Deuteronomy 22:22
Also death if betrothed and in a city:
“If a damsel that is a virgin be betrothed unto an husband, and a man find her in the city, and lie with her; Then ye shall bring them both out unto the gate of that city, and ye shall stone them with stones that they die; the damsel, because she cried not, being in the city; and the man, because he hath humbled his neighbour's wife: so thou shalt put away evil from among you. - Deuteronomy 22:23-24
This last one is interesting because perhaps this is what Joseph was thinking happened (Mary had just gone to the “country” to visit Elizabeth.
And no death if betrothed, but it happened in the country:
“But if a man find a betrothed damsel in the field, and the man force her, and lie with her: then the man only that lay with her shall die: But unto the damsel thou shalt do nothing; there is in the damsel no sin worthy of death: for as when a man riseth against his neighbour, and slayeth him, even so is this matter: For he found her in the field, and the betrothed damsel cried, and there was none to save her. - Deuteronomy 22:25-27
If Joseph thought this last case might have happened, then what is the whole “make a public example” about since there is no fault of her’s here? Also, how could he legally divorce her (even quietly)? Perhaps he ascribed to the standard teaching Jesus refuted about divorce for any reason?