"(We also sent) Lut (as a messenger): behold, He said to his people, "Do ye do what is shameful though ye see (its iniquity)? Would ye really approach men in your lusts rather than women? Nay, ye are a people (grossly) ignorant! But his people gave no other answer but this: they said, "Drive out the followers of Lut from your city: these are indeed men who want to be clean and pure!" Then We saved him and his household save his wife; We destined her to be of those who stayed behind. And We rained down on them a shower (of brimstone): and evil was the shower on those who were admonished (but heeded not)! - Quran 27:54 (read more)

"Narrated 'Abdullah bin 'Umar : The Jew brought to the Prophet a man and a woman from amongst them who have committed (adultery) illegal sexual intercourse. He ordered both of them to be stoned (to death), near the place of offering the funeral prayers beside the mosque." - Sahih Bukhari 7:62:64 (read more)

"The actual example of one of the greatest Companions, `Ali ibn Abi Talib (may Allah be pleased with him) gives credit to this [death sentence for apostasy] also. He himself carried out the punishment on some people who had deified him. He gave them three days respite to repent and go back to their senses. When they proved adamant, he put them to fire." - IslamOnline