Narrated by Abu Huraira (Radiyallahu `anhu) that the Prophet (Sallallaahu `alayhi wa sallam) said,
“If any one of you says, ‘Ameen’ and the angels in the heavens say ‘Ameen’ and the former coincides with the latter, all his past sins will be forgiven.”

Narrated Anas bin Malik (Radiyallaahu `anhu),
“Once in the lifetime of the Prophet (p.b.u.h) the people were afflicted with drought (famine). While the Prophet was delivering the Khutba on a Friday, a Bedouin stood up and said, “O, Allah’s Apostle! Our possessions are being destroyed and the children are hungry; Please invoke Allah (for rain)”.