Sayyiduna Abu Bakrah (may Allah be pleased with him) narrates that the Prophet Muhammad (peace and blessings be upon him) said: "There is no sin more deserving that Allah punishes its doer in this world, and also prepares punishment for him in the Hereafter, than severing ties of kinship and committing adultery."
Hadith Referenceصحیح ابن حبان / كتاب البر والإحسان / 456
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - انظر ما قبله.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح.