The hadeeth of two men from amongst the companions, from the Prophet (salallaahu ‘alayhi wa sallam):
“Whoever says, ‘Laa illaaha ilallaahu wahdahu la shareekalahu lahul mulku wa lahul hamdu wa Huwa ‘ala kulli Shay’`in Qadeer’ with a sincere heart, attesting to the truth of that with his tongue, then Allaah will surely tear open the sky until He looks at the person from amongst the people of the earth who said it. And the right of the servant whom Allaah looks at is that He grants him whatever he asked for.” (An-Nisaee)
There Also occurs upon the authority of Abu Huraira (Radhiyallahu ‘anhu) who said that the messenger (Sallallahu alahi wa salam) who said:
“No servant says Laa ilaha illallah sincerely, except that the heavens open up for it and it ascends until it reaches the throne, providing one stays away from the major sins”