…Verily, for all believers prayer is indeed a sacred duty linked to particular times [of day]. -- Q.4: 103
…Say : “Verily, God’s guidance is the only guidance: and so we have been directed to surrender ourselves unto the Sustainer of all the worlds, and to be constant in prayer and conscious of Him: for it is He unto whom you all shall be gathered.” -- Q.6:71--72
Prophet said
When asked which action was best the Messenger of God said: “Prayer in its initial time” – H: Ahmed, Tirmizi and Abu Daud. N: Omme Farwah
“To offer prayer early in time is to please God and to offer prayer late in time is to ask God’s forgiveness” – H: TIrmizi. N: Ibn Umar.
“The first action for which a servant (of God) will be taken into account on the Resurrection Day will be his prayer” -- H: Abu Daud and Ahmed. N: Abu Hurairah
The Prophet called (a man who had committed a sin) and recited the verse 11:114 of the Qur’an. (See the last verse of this topic.) Someone asked: O Apostle of God! Is it specially for Him? He replied: “Rather for the whole mankind.” – H: Muslim. N: Abdullah-b-Masud