Allah, the Mighty and Majestic, says: "O you who believe, do not nullify your charity by reminders of generosity and by injury." [Surah al-Baqarah: 264]
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / Q7841
Sayyiduna Abu Dharr (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "There are three to whom Allah Almighty will not speak on the Day of Resurrection, nor look at them, nor purify them, and for them is a painful punishment: the one who reminds others of what he gave, the one who lets his lower garment hang down, and the one who sells his goods with a false or wicked oath."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الزكاة / 7841