Sahih Al Bukhari – Book of Good Manners And Form (Al-Adab)
Volumn 008, Book 073, Hadith Number 017.
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Narated By Abu Huraira : The Prophet said, "The word 'Ar-Rahm (womb) derives its name from Ar-Rahman (i.e., one of the names of Allah) and Allah said: 'I will keep good relation with the one who will keep good relation with you, (womb i.e. Kith and Kin) and sever the relation with him who will sever the relation with you, (womb, i.e. Kith and Kin).