After four years: The Hebrew text says forty years, which would place Absalom’s rebellion in David’s final year as king, causing many timeline issues with later events (also see study note on 2 Samuel 15:1–19). The Greek and Syriac versions are more likely accurate.
fulfill a vow: This offering was to keep a promise to God, unlike a freewill offering given out of devotion and gratitude (see Genesis 28:20–22; Judges 11:30–31; 1 Samuel 1:11). Absalom was probably lying (compare 1 Samuel 20:28–29).