The Salat is the most important act of worship in Islam, and if it is accepted by Allah (SWT), then all other acts of worship are accepted as well. However, if the Salat is not accepted, then all other actions also will not be accepted. It has been narrated from the 6th Imam, Ja 'far ibn Muhammad as-Sadiq, peace be upon him, quoting his forefathers up to the Messenger of Allah, peace be upon him and his family, that he said:
“If there was a strem at the house of any one of you in which he washes himself five times a day, will ther remain any dirt on your body? Verily, the likeness of the Salat is the same as the stream. The Person who establishes the ritual prayers clears out his sins thereby, execpt for the sin that take him out from the faith that he believes in”. (Bihar al-Anwar, Vol. 82, Pg. 236)