Taysalah bin Ali said: I asked Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) on the day of Arafah, while he was at the foot of an arak tree pouring water over his head and face. I said to him: May Allah have mercy on you, tell me about the major sins. He said that the Messenger of Allah (peace and blessings be upon him) said: "The major sins are associating partners with Allah and slandering a chaste woman." I said: Is killing (also a major sin)? He said: "Yes, even if you dislike it; and killing a believing soul, fleeing from the battlefield, consuming the wealth of an orphan, disobeying Muslim parents, and violating the sanctity of the Sacred House, which is the qiblah of your living and your dead."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنائز / 6724