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
At the last moments of his life, Imam as-Sadiq (‘a) called his relations and companions and told them: "Verily, our intercession never reaches the one who takes prayers lightly."
Bihar-ul-Anwar, vol. 82, p. 236
Imam al-Baqir, the fifth Imam, (‘a) said: "There are ten things that when a person meets Allah the Almighty and Glorious, with them, he will enter Heaven:
1. Confessing that there is no god besides Allah
2. And that Muhammad is the Messenger of Allah
3. Acknowledging what has come down to the Prophet (S) from Allah (the Qur'an).
4. Establishing regular prayers.
5. Giving alms.
6. Fasting in Ramadan.
7. Performing the Pilgrimage (Hajj) to the Sacred House.
8. Kindness to the lovers of Allah
9. Detachment from the enemies of Allah
10. And, avoiding any alcoholic beverage."
Khisal by Saduq, p.432
Imam Amir ul Mu'mineen ‘Ali (‘a) said: "For the God-fearing, prayer is a means of seeking nearness to Allah and for the weak, the Hajj (pilgrimage to Mecca) is as good as Jihad (fighting in the way of Allah). For every thing there is a levy, and the levy of the body is fasting. The Jihad of a woman is to afford pleasant company to her husband."
Nahjul Balagha, saying 136
The Holy Prophet (S) said: There comes no night but that the angel of death calls to the dead in the graves and inquires what they regret for today when they have vividly seen (and known) this (the next life). Then the dead will say: "Verily, we regret and envy the believers who are in their mosques and they are praying while we are not; they give alms and we do not; they fast during Ramadan but we do not; they donate in charity what they have more than the need of their family members while we do not; ..."
The Holy Prophet (S) said: "At the (appointed) time of every prayer (salat), I hear a caller who calls and says: "O children of Adam! Keep up prayers in order to extinguish the fire you have lit against yourselves (by committing sins)."
Mustadrak-ul-Wasa'il, vol. 3, p. 102
The Holy Prophet (S) said: "Be careful of the prayers, for, on the Day of Resurrection, when Allah the Exalted, will bring the servant (for reckoning), the first thing that He will ask him about will be the prayer. If one brings it completely, he will be of the people of salvation, otherwise, he will be thrown into Fire."
Bihar-ul-Anwar, vol. 82, p. 202
Abubasir said that he visited Umm Hamidah (Musa-ibn Ja'far's (‘a) mother) in order to console her for the death of Ja'far-ibn-Muhammad (‘a). Then she wept and he wept because of her weeping. After that, she said: "O' Aba Muhammad! If you had seen Ja'far-ibn-Muhammad when he was on his death-bed, you would have observed a wonderful thing: he opened his eyes and said to gather all of his relatives." Then, she continued saying that they gathered them all with no exception. Then he (‘a) looked at them and said: "Verily, our intercession does not reach the one who takes prayers lightly".
Wasa'il-ush-Shi'ah vol. 4, p. 26
The Holy Prophet (S) said: "The worship done by the one who earns his living on unlawful money is similar to a building constructed upon sand."
Bihar-ul-Anwar, vol. 84, p. 258