Background
The answer is found in the New Testament:
Accounting that God is able to raise up even from the dead. Whereupon also he received him for a parable. (Hebrews 11:19 DRA)
λογισάμενος ὅτι καὶ ἐκ νεκρῶν ἐγείρειν δυνατὸς ὁ θεός ὅθεν αὐτὸν καὶ ἐν παραβολῇ ἐκομίσατο
The basic sense of a parable is a side-by-side comparison of two things:
The word ‘parable’ is simply the English form of a quite common Greek word (parabolē) which in ordinary Greek usage meant the putting of one thing alongside another by way of comparison or illustration. Aristotle, for example, defines the word as meaning ‘comparison’ or ‘analogy’. (Rhet. 11, xx, 2-4). But in the Greek Bible the meaning of the word is affected by the meaning of the Hebrew word māšhāl Aramaic: məethel) which it was used to translate; and as a māšhāl has a number of uses, so in biblical Greek does the word ‘parable’.1
The "parable" of the Akedah (the binding) of Isaac, is the comparison with the offering of Jesus. Here are a few parallels:
Abraham offers Isaac The Father offers Jesus
Isaac is bound before he is offered Jesus is bound before He is offered
Two servants do not go with Isaac Two thieves go with Jesus
The angel of the LORD stops Abraham Jesus does not stop Pilate
The LORD will provide a lamb Jesus is the Lamb
Some comparisons are the same; some are antithetic.
Three Days
It took Abraham and Isaac three days to travel from Beersheba (v. 22:19) to Mount Moriah:
3 So Abraham rose early in the morning, saddled his donkey, and took two of his young men with him, and his son Isaac. And he cut the wood for the burnt offering and arose and went to the place of which God had told him. 4 On the third day Abraham lifted up his eyes and saw the place from afar. (Genesis 22 ESV)
On the third day after leaving Beersheba, Abraham lifted his eyes and saw the place. Afterward, Abraham returned to Beersheba. Not only is Isaac "missing" from the narrative, there is no mention of the length of time the trip took. However, if Abraham was able to see the place of sacrifice on the third day, then it is reasonable to conclude he would see Beersheba on the third day when returning.
Therefore, Isaac and the travel time have been intentionally omitted from the narrative in Genesis in order to form a more perfect comparison with the offering of Jesus:
Isaac "disappears" from the next 3-days Jesus "disappears" from the next 3-days
After He was crucified, Jesus "disappears" from the Gospel accounts: just as there is no mention of Isaac on the return trip. But, on the third day He returns to the same place He had been left. Therefore, if Isaac did return, which is most likely, the comparison of that location is antithetic. Regardless, the narrative in Genesis has been intentionally crafted to be compared with the crucifixion of Jesus.
In addition, most scholars believe the offering of Isaac took place at the place where the Temple was built. f that is correct, the location of the two is another component of the parable.
1. D.E. Nineham, The Gospel of St. Mark, The Seabury Press, 1963 p. 126