Charles Ellicott Commentary 1 Samuel 1:21

"And the man Elkanah, and all his house, went up to offer unto Jehovah the yearly sacrifice, and his vow." — 1 Samuel 1:21 (ASV)

And his vow. —Elkanah too had vowed a vow unto the Lord, in case his wife Hannah should have a son. It has been remarked that vows are characteristic of that particular age of the Judges; for instance, we have detailed accounts of Samson and Jephthah’s vows, the oath in the Benjamite vow, etc.