Repentance from viewpoint of reason and tradition

Nobody achieves to any grade of accomplishment, lack sin in a general meaning. For this, repentance has been introduced a common obligation in Quran. Although from the viewpoint of religion, every man must avoid from sin; but if he sin, he can save by repenting.
In this writing, I have tried to set forth some most important problems of repentance in two general sections: in first section, some Moslem scholar’s opinion and in second section I have tried to search emam sajjad’s (peace be upon him) opinion about repentance and tried to study some its important problems.