It is narrated from Sayyiduna Talhah (may Allah be pleased with him); he said: The Messenger of Allah (peace and blessings be upon him) said: "Whoever is shown a kindness, let him mention it; whoever mentions it has thanked it, and whoever conceals it has been ungrateful for it."
Hadith Referenceالمعجم الكبير للطبراني / العشرة / 210