«ما من امرئ مسلم تحضره صلاة مكتوبة فيحسن وضوءها وخشوعها وركوعها إلا كانت كفارة لما قبلها من الذنوب ما لم تؤت كبيرة وذلك الدهر كله»
The Prophet (peace and blessings be upon him) said:
"There is no Muslim man who, when an obligatory prayer comes due, performs its ablution, its humility and its bowing well, except that it becomes an expiation for the sins before it, as long as no major sin is committed; and that is for all time."
Hadith Referenceصحیح الجامع الصغیر / حرف الميم / 5686