by St. Nikolai Velimirovich
To take another's sin upon one's self, that is one form of martyrdom and the sign of one's overwhelming love for one's fellow man.
As death is the consequence of sin, to take another's sin on one's self means to add to your own death still another death, "And sin, when it is finished, brings forth death" (James 1:15). However, God rewards with resurrection those who, out of love, take another's death upon themselves.
There are many examples how the saints took upon themselves the sins of their fellow men. Thus, it is said of St. Ammon: a brother fell into sin and came to Ammon and said to him that because of the sin he committed, he must leave the monastery and return to the world. Ammon said to the brother that he will take his sin upon himself and counseled the brother to remain in the monastery. The brother remained in the monastery and the elder Ammon proceeded to offer repentance and prayers to God. After a short time, the elder Ammon received a revelation from God that that sin is forgiven because of his love for the brother.
When St. Macarius, St. Symeon the "fool for Christ", St. Theodora and others were accused of promiscuity, they did not defend themselves but, taking upon themselves the sin of others, received the weighty punishment for sin and patiently endured all until God revealed their innocence to men.