It is narrated from the prophet of Islam (PBUH) who said: Allah (SWT) told Hazrat Dawood (AS): Give glad tidings to the sinners and warn the pious. Hazrat Dawood (AS) asked: Oâ€™ Allah (SWT) how do I give glad tidings to the sinners and warn the pious? Allah (SWT) replied: Oâ€™ Dawood, give glad tidings to the sinners that I will accept their repentance and will pardon the sinners, and warn the pious not to become proud and deluded with their prayers; all servants of God will be made to account (for all their deeds) .
 Osoule Kafi, Vol. 3, page 429.