When you do not do what you have promised to God because it is too disadvantageous for you, you place the guilt of sin on yourself. You bring God's wrath upon your life. The disadvantage of this is much greater than carrying out your vow anyway. By carrying out your vow your life will not suffer eternal destruction. Then your life and work will not be ruined forever.
6 Let not your mouth lead you into sin, and do not say before the messenger that it was a mistake. Why should God be angry at your voice and destroy the work of your hands?