Surely Allah is not ashamed to set forth any parable-- (that of) a gnat or any thing above that; then as for those who believe, they know that it is the truth from their Lord, and as for those who disbelieve, they say: What is it that Allah means by this parable: He causes many to err by it and many He leads aright by it! but He does not cause to err by it (any) except the transgressors,
Al-Baqra Verse 26
Allah's Apostle said, "If anyone of you enters a mosque, he should pray two Rakat before sitting."
Sahih Bukhari: Volume 1, Book 8, Number 435