Imam al-Sadiq (a) said,
“The first thing that a servant shall be reckoned for (on the Day of Judgment) shall be his prayers. If they are accepted, all his other deeds shall be accepted too and if they are rejected, the other deeds shall be rejected too!”
[Falah al-sa'il. P.127.]...
When the police stop a driver on the road, they request the drivers licence from the driver. If the driver presents a doctor licence, political licence, builders licence, business approval documents and licence of “ijtihad”, or whichever other documents one can present, the police will not accept this from the driver. The only document the police will accept will be the drivers licence; otherwise, he will prevent the driver from proceeding.
In the Resurrection also, it is a condition that to be able to reach your destination, your Prayer Licence needs to be with you and if not, none of the other documents or deeds you have will be accepted or give you salvation.[1]
Perhaps, the reason could be that the prayer is the key towards establishing a connection between the Creator and the creation, and if offered correctly, would generate within him sincerity and the intention of attaining nearness to Allah - the two factors that are the means for the acceptance of deeds. But if not, then all his other deeds become tainted, and thus drop from reckoning.
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1)Important Questions – Simple Answers. written by Muhsin Qara'ati