When we make a pledge, the Lord takes that seriously, as if it's already a done deal. When we pledge our lives to the Lord, he will do everything he can to help us fulfill it, but there remains responsibility on our part. Genesis 19 shares how two angels, posing as men, came to Lot to warn him of judgement that was about to come on Sodom and Gomorrah. The angels asked Lot if he had any sons-in-law in the city, so that they too could get to safety. There were two men who were pledged to marry Lot's daughters, but they weren't married yet. Lot went and told them that the city would be destroyed, but they thought he was joking. Either these two men were given over to the same perversion as the rest of the men in the city, or they didn't think God would do such a thing. Either way, I think it's fair to say that they weren't in tune with God and how he is a merciful, but just God. The Lord was willing to spare two men who weren't officially part of Lot's family, but who had made pledges to marry into the family.
Genesis 19:12-15 shares this with us.
The two men said to Lot, “Do you have anyone else here—sons-in-law, sons or daughters, or anyone else in the city who belongs to you? Get them out of here, because we are going to destroy this place. The outcry to the Lord against its people is so great that he has sent us to destroy it.” So Lot went out and spoke to his sons-in-law, who were pledged to marry his daughters. He said, “Hurry and get out of this place, because the Lord is about to destroy the city!” But his sons-in-law thought he was joking. With the coming of dawn, the angels urged Lot, saying, “Hurry! Take your wife and your two daughters who are here, or you will be swept away when the city is punished.” - Genesis 19:12-15