The Holy Prophet (S) said: “The one who takes prayer light is not of me. No, by Allah such a person will not reach the Haud, Pond of abundant.” - Man La Yahduruhul Faqih, vol. 1, p. 206
Imam as-Sadiq (‘a) said: “If there be a stream at the house of one of you in which the one washes himself five times a day, will there remain anything from the dirt over his body? Verily, the likeness of prayers is the same as the stream. The person who establishes ritual prayers clears out his sins thereby, except for the sin that takes him out from Faith he believes in.” - Bihar-ul-Anwar, vol. 82, p. 236
The Holy Prophet (S) said: An obligatory prayer, with Allah, is equivalent to one thousand Hajj pilgrimages and one thousand Umrah performances (voluntary pilgrimages to Ka’ba) which are right and accepted." - Bihar-ul-Anwar, vol. 99, p. 14
The Holy Prophet (S) said: “Do not waste your prayers, because, surely, the person who wastes them will be raised with Croesus (Qarun) and Haman so that it is rightfully certain for Allah to put the one in Hell with hypocrites.” - Bihar-ul-Anwar, vol. 83, p. 14
The Holy Prophet (S) said: “Say each of your prayer as if it were your last prayer.” - Bihar-ul-Anwar, vol. 69, p. 408
Imam Amir ul Mu’mineen ‘Ali (‘a) said: “If a praying person knew to what extent he was surrounded by His Mercy, he would never raise his head from (the state of) prostration. - Tasnif al-Ghurar-ul-Hikam, p. 175
Imam al-Baqir (‘a) said: “On the Reckoning Day, the first thing that a servant will be reckoned for is the prayer; therefore, if it is accepted, the rest (good actions) will be accepted, too, (otherwise, his other good deeds will not avail him).” - Bihar-ul-Anwar, vol. 7, p. 267
Source:
A Bundle of Flowers [P 13-14].
Amir al-Mu’mineen Ali (a.s.) Library