ENOfficial
‘Abdullah ibn al-Harith ibn Jaz said (may Allah be well pleased with him): "I have not seen anyone with a more cheerful countenance than Allah's Messenger (Allah bless him and give him peace)!"
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، قَالَ: أَخْبَرَنَا ابْنُ لَهِيعَةَ، عَنْ عُبَيْدِ اللهِ بْنِ الْمُغِيرَةِ، عَنْ عَبْدِ اللهِ بْنِ الْحَارِثِ بْنِ جَزْءٍ، أَنَّهُ قَالَ: مَا رَأَيْتُ أَحَدًا أَكْثَرَ تَبَسُّمًا مِنْ رَسُولِ اللهِ صلى الله عليه وسلم..
sunnah.com