Musnad Abu Ya'la al-Mawsili 111:139

Ubayd Allah ibn Umar narrated to us, Mu'tamir narrated to us, from his father, from Hanash, from Ikrimah, from Ibn Abbas, from the Prophet (peace and blessings of Allah be upon him), who said: "Whoever combines two prayers without an excuse has approached a gate from the gates of major sins." And whoever—meaning—conceals testimony, and by it destroys the wealth of a Muslim man or sheds his blood, has made the Fire mandatory, or as he said.