At thirty verses, Vayelech is among the shortest of the fifty-four weekly portions, yet its brief span sets up the whole of the portion that follows it: God tells Moses that after his death the people will break the covenant, and instructs him to write down a poem, 'this song,' as a witness that will testify against Israel once the warning is forgotten (Deuteronomy 31:19-22), a poem the Torah then supplies in full as the very next portion, Haazinu. Vayelech is therefore less a self-contained unit than a structural hinge, its brevity a function of handing off almost immediately to the text it introduces.
Moses' charge to Joshua, 'be strong and of good courage... for the Lord your God, He it is that goes with you' (Deuteronomy 31:7-8, repeated again at 31:23), is echoed almost word for word at the very opening of the following book, when God repeats nearly the same charge directly to Joshua (Joshua 1:6-9), a deliberate verbal bridge many literary scholars read as marking Joshua's leadership as authorised twice over, once by Moses' own blessing here and once, immediately after, by direct divine confirmation opening the next book of the Bible.
Its warning that Israel will one day forsake the covenant is read, in most years, in the days immediately surrounding Rosh Hashanah, a placement commentators find thematically apt for the season of self-examination that opens the Jewish new year, even though the specific pairing with the preceding or following portion shifts from year to year depending on the calendar.