Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) reports this saying of the Prophet (peace and blessings be upon him): "After the obligatory duties, the most beloved deed to Allah Almighty is bringing joy to a Muslim."
Al-Tabarani recorded it in al-Mu'jam al-Awsat; its chain contains a narrator, Isma'il bin Amr al-Bajali, whom Ibn Hibban declared thiqah (trustworthy), while others called him da'if (weak).