Sahih Bukhari
To make the Heart Tender (Ar-Riqaq)
Volume: 008 / Book Number: 076 / Hadith Number: 432
Narrated Abu Huraira: Allah's Apostle said, "Allah says, 'I have nothing to give but Paradise as a reward to my believer slave, who, if I cause his dear friend (or relative) to die, remains patient (and hopes for Allah's Reward)."