"It is dangerous... to make a vow and have second thoughts." (From Prov 20:25 NEB).
BEFORE MAKING A VOW, GIVE IT DUE
"Do not rush into speech, let there be no hasty utterance in God's presence. God is in heaven, you are on earth; so let your words be few... When you make a vow to God, do not be slow to pay it, for He has no use for fools; pay whatever you vow. Better not vow at all than vow and fail to pay. Do not let your tongue lead you into sin, and then say before the angel of God that it was a mistake; or God will be angry at your words, and all your achievements will be brought to nothing. You must fear God." (From Eccles 5:2 & 4-7 NEB).
"Let nothing hinder the prompt discharge of your vows; do not wait till death to be absolved. (2) Before you make a vow, give it due thought; do not be like those who try the Lord's patience. Think of the wrath you must face in the hour of death, when the time of reckoning comes, and He turns away His face." (Eccus 18:22-24 NEB).