Musannaf Ibn Abi Shayba 33:1365

Al-Hasan ibn Musa narrated to us, he said: Hammad ibn Salamah narrated to us, from Thabit al-Bunani, from Mutarrif ibn Abdullah ibn al-Shikhkhir, who said: "Whoever purifies [his deeds] for Him, it is purified for him; and whoever mixes [his deeds], it is mixed against him."