Abu Salih (may Allah have mercy on him) narrates from Sayyiduna Abdullah bin Abbas (may Allah be pleased with him) that a man named Salih came with his brother and said: "O Messenger of Allah! I want to free this brother of mine." He (peace and blessings be upon him) said: "He became free the very moment you became his owner."
Ali al-Daraqutni (may Allah have mercy on him) said: Al-Arzami was abandoned by Ibn al-Mubarak, Yahya al-Qattan and Ibn Mahdi. And Abu al-Nadr is Muhammad bin al-Sa'ib al-Kalbi, who is matruk (abandoned); and he is also the one who said: Everything I have narrated from Abu Salih is a lie.
The Shaykh (may Allah have mercy on him) said: It is also narrated from Hafs bin Abi Dawud, from Muhammad bin Abi Layla, from Ata, from Ibn Abbas in similar words, and this chain is weak; Hafs is Ibn Sulayman al-Qari, whom Shu'bah, Ahmad bin Hanbal, Yahya bin Ma'in and others declared weak.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب العتق / 21421