Sahih Bukhari Volume 8, Book 73, Hadith Number 18.
Narated By ‘Aisha : (The wife of the Prophet) The Prophet said, “The word ‘Ar-Rahm’ (womb) derives its name from ‘Ar-Rahman’ (i.e. Allah). So whosoever keeps good relations with it (womb i.e. Kith and kin), Allah will keep good relations with him, and whosoever will sever it (i.e. severs his bonds of Kith and kin) Allah too will sever His relations with him.