When God sent angels to punish the people of Lot, they stopped by Prophet Abraham to give him the good news of the birth of Isaac. He was happy, but when he came to know that angels are going to punish the people of Prophet Lot, he pleaded to them to spare them. Below is the story from The Quran:
And certainly did Our messengers come to Abraham with good tidings; they said, "Peace." He said, "Peace," and did not delay in bringing [them] a roasted calf. (69) But when he saw their hands not reaching for it, he distrusted them and felt from them apprehension. They said, "Fear not. We have been sent to the people of Lot." (70) And his Wife was standing, and she smiled. Then We gave her good tidings of Isaac and after Isaac, Jacob. (71)
She said, "Woe to me! Shall I give birth while I am an old woman and this, my husband, is an old man? Indeed, this is an amazing thing!" (72) They said, "Are you amazed at the decree of Allah? May the mercy of Allah and His blessings be upon you, people of the house. Indeed, He is Praiseworthy and Honorable." (73)
And when the fright had left Abraham and the good tidings had reached him, he began to argue with Us concerning the people of Lot. (74) Indeed, Abraham was forbearing, grieving and [frequently] returning [to Allah]. (75)
[ How Seeing is He and how Hearing! They have not besides Him any protector, and He shares not His legislation with anyone." (The Quran, 18:26) ]
[The angels said], "O Abraham, give up this [plea]. Indeed, the command of your Lord has come, and indeed, there will reach them a punishment that cannot be repelled." (76) And when Our messengers, [the angels], came to Lot, he was anguished for them and felt for them great discomfort and said, "This is a trying day." (77) And his people came hastening to him, and before [this] they had been doing evil deeds. He said, "O my people, these are my daughters; they are purer for you. So fear Allah and do not disgrace me concerning my guests. Is there not among you a man of reason?" (78) They said, "You have already known that we have not concerning your daughters any claim, and indeed, you know what we want." (79) He said, "If only I had against you some power or could take refuge in a strong support." (80) The angels said, "O Lot, indeed we are messengers of your Lord; [therefore], they will never reach you. So set out with your family during a portion of the night and let not any among you look back - except your wife; indeed, she will be struck by that which strikes them. Indeed, their appointment is [for] the morning. Is not the morning near?" (81)
So when Our command came, We made the highest part [of the city] its lowest and rained upon them stones of layered hard clay, [which were] (82) Marked from your Lord. And Allah 's punishment is not from the wrongdoers [very] far. (83)
The Quran, Chapter 11, Except where noted otherwise
Translation from http://tanzil.net