We are never told about Elkanah making a vow. Possibly it could refer to a commitment on his part to make an annual pilgrimage to Shiloh in order to sacrifice before the Lord. In the context of the chapter, however, it most likely refers to the vow which Hannah has made (1 Samuel 1:11).1 Having told her husband about her vow, he had the option of approving or rescinding it (see Numbers 30:1–16).2 In this case Elkanah has approved of the vow so that it is now his vow and he wants to see it fulfilled as soon as possible (see Deuteronomy 23:21–23).3
21 The man Elkanah and all his house went up to offer to the LORD the yearly sacrifice and to pay his vow.