Sayyiduna Abu Hurayrah (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) climbed the pulpit and said: "Amin, amin, amin." It was said to him: You did not use to do this? He (peace and blessings be upon him) said: "Jibril, the Trustworthy, said to me: May the nose of the person be rubbed in dust upon whom the month of Ramadan came and he did not have himself forgiven. So I said: Amin. Then he said: May the nose of the person be rubbed in dust in whose presence you are mentioned and he does not send blessings upon you. So I said: Amin. Then he said: May the nose of the person be rubbed in dust who found his parents, both or one of them, and then did not enter Paradise because of them. So I said: Amin."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 8504