Unto Him belongs all that is in the heavens and all that is on earth; and, verily, God - He alone - is self-sufficient, the One to whom all praise is due.
Al-Hajj (The Pilgrimage) Verse 64
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