Genesis 18:21

I will go down now and see whether they have done altogether according to the cry of it which is come unto Me; and if not, I will know. The sins of Sodom and Gomorrah were of a nature to cry to heaven for revenge and punishment: "The cry about Sodom and Gomorrah yea, it is great; and their sin truly it is very heavy!" The Lord's purpose, therefore, was to convince Himself whether the inhabitants of these cities, according to the cry that had come to Him, had reached the limit of wickedness or not. It was a case of mercy's meeting together with righteousness.