Should a filthy rag vow? If so, pay that which thou hast vowed

Ecclesiastes 5:4-6 KJV When thou vowest a vow unto God, defer not to pay it; for he hath no pleasure in fools: pay that which thou hast vowed. [5] Better is it that thou shouldest not vow, than that thou shouldest vow and not pay. [6] Suffer not thy mouth to cause thy flesh to sin; neither say thou before the angel, that it was an error: wherefore should God be angry at thy voice, and destroy the work of thine hands?