وَعَنْ كَعْبِ بْنِ مَالِكٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا سُرَّ اسْتَنَارَ وَجْهُهُ حَتَّى كَأَنَّ وَجْهَهُ قِطْعَةُ قَمَرٍ وَكُنَّا نَعْرِفُ ذَلِكَ. مُتَّفَقٌ عَلَيْهِ
Ka'b b. Malik said: When God's messenger was pleased his face lit up so that it looked like a bit of a moon, and we were familiar with that. (Bukhari and Muslim.)