Ecclesiastes 5:4

When thou vowest a vow unto God The words are almost a reproduction of Deuteronomy 23:22-24. They point to a time when vows, such as are here referred to, entered largely into men's personal religion. Memorable instances of such vows are found in the lives of Jacob (Genesis 28:20), Jephthah (Judges 11:30), Saul (1 Samuel 14:24). In later Judaism they came into a fresh prominence, as seen especially in the Corban of Mark 7:11, the revival of the Nazarite vow (Acts 18:18; Acts 20:23; Joseph. Warsii. 15, p. 1), and the oath or anathema of Acts 23:21; and one of the treatises of the Mishna (Nedarim) was devoted to an exhaustive casuistic treatment of the whole subject. In Matthew 5:23 we find the recognised rule of the Pharisees, "Thou shalt perform unto the Lord thine oaths," as the conclusion of the whole matter. This the Debater also affirmed, but he, in his deeper wisdom, went further, and bade men to consider well what kind of vows they made.

for he hath no pleasure in fools The construction of the sentence in the Hebrew is ambiguous, and may give either (1) that suggested by the interpolated words in the A. V., or (2) " there is no pleasure in fools," i.e. they please neither God nor man, or (3) " there is no fixed purpose in fools," i.e.they are unstable in their vows as in everything else. Of these interpretations (2) has most to commend it. In Proverbs 20:25, "It is a snare … after vows to make inquiry," we have a striking parallel.