Hadeeth Qudsi 9:

On the authority of AbuHarayrah (may Allah be pleased with him) from the Prophet ,who said: Allah (mighty and sublime be He) says:

The fist of his actions for whicha servant of Allah will be held accountable on the Day of Resurrectionwill be his prayers. If they are in order, then he will have prosperedand succeeded: and if they are wanting, then he will have failed andlost. If there is something defective in his obligatory prayers, theLord (glorified and exalted be He) will say: See if My servant has anysupererogatory prayers with which may be completed that which wasdefective in his obligatory prayers. Then the rest of his actions willbe judged in like fashion.

It was related by at-Tirmidhi(also by Abu Dawud, an-Nasa’i, Ibn Majah and Ahmad).