Musnad Ahmad 10:32

Yazid ibn Harun narrated to us, Hisham informed us, from Yahya ibn Abi Kathir, from Ibrahim ibn Abdullah ibn Qariz, that his father narrated to him that he entered upon Abd al-Rahman ibn Awf while he was ill. Abd al-Rahman said to him, "May you maintain kinship, for the Prophet, peace and blessings of Allah be upon him, said: 'Allah said: I am the Rahman (the Most Merciful), and I created the womb (rahim) and derived for it a name from My name. Whoever maintains it, I will maintain him, and whoever severs it, I will sever him' — or he said: 'Whoever cuts it off, I will cut him off.'"