Musnad Abu Ya'la al-Mawsili 155:113

And from Abu Hurayrah, from the Prophet, may Allah bless him and grant him peace, that he said: Allah said: "I am the Most Merciful (al-Rahman), and it is the womb (al-rahim). I have derived its name from My name. Whoever maintains it, I maintain him, and whoever severs it, I sever him."