Sayyiduna Abu Hurayrah (may Allah be pleased with him) reports this saying of the Prophet (peace and blessings be upon him): "When a man says to his brother, 'May Allah Almighty reward you with good,' he has praised him fully."
Imam al-Bazzar recorded it, and its chain contains a narrator, Musa bin Ubaydah, who is da'if (weak).
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب البيوع / 6738