With this same chain, it is narrated from the Messenger of Allah (peace and blessings be upon him), he said: "Tell me, what do you think about the adulterer, the thief, and the one who drinks alcohol?" They replied: Allah and His Messenger know best. He (peace and blessings be upon him) said: "They are evil and there is punishment for them." Then he said: "Shall I not tell you about the gravest of sins?" They replied: Allah and His Messenger know best. He (peace and blessings be upon him) said: "Associating partners with Allah, harming one's parents, speaking falsehood, killing a Muslim, and slandering a chaste woman."
Hadith Referenceمسند اسحاق بن راهويه / كتاب الايمان / 60