Why does the Torah provide two different accounts of the borders that are to define Israel; each border fairly different than the other? (Shemos 23:31 and Bamidbar 34:2)
Thanks for asking this question. This question is a great one because there does seem to be a contradiction. When the verses are read more carefully though, the resolution is clear. The passage in Bamidbar is speaking of the land when Yehoshua conquers it and is consistent until the time of the first Temple period. In the book of Shemos (and Genesis 15:18 & Deuteronomy 1:7) it is speaking of the land of Israel in the days of the Messiah. This is according to a commentator called the Tevuos HaAretz.
So, The biblical land of Israel that we have rights to now is consistent with the delineation in Bamidbar 34:2. However, we will move further when the time is right. (G-d willing, it should be soon).
Be Well,
Rabbi Litt