SB 11.20.25

yadi kuryāt pramādena
 yogī karma vigarhitam
yogenaiva dahed aṁho
 nānyat tatra kadācana
Synonyms: 
yadi — if; kuryāt — should perform; pramādena — due to negligence; yogī — the yogī; karma — an activity; vigarhitam — abominable; yogena — by the yoga process; eva — only; dahet — he should burn up; aṁhaḥ — that sin; na — no; anyat — other means; tatra — in this matter; kadācana — at any time (should be employed).
Translation: 
If, because of momentary inattention, a yogī accidentally commits an abominable activity, then by the very practice of yoga he should burn to ashes the sinful reaction, without at any time employing any other procedure.
Purport: 

The word yogena here indicates jñānena yogena and bhaktyā yogena, since these two transcendental systems have the power to burn sinful reactions to ashes. It should be clearly understood that the word aṁhas, or “sin,” here refers to an accidental falldown against one’s desire. Premeditated exploitation of the mercy of the Lord can never be excused.

Significantly, the Lord forbids any extraneous purificatory rites, since the transcendental yoga systems are themselves the most purifying processes, especially bhakti-yoga. If one gives up one’s regular prescribed duties to perform a special ritual or penance, trying to purify a sinful reaction, then one will be guilty of the additional fault of giving up one’s prescribed duties. One should pick oneself up from an accidental falldown and go on vigorously with one’s prescribed duties in life without being unnecessarily discouraged. One should certainly lament and feel ashamed, or there will be no purification. However, if one becomes overly depressed at an accidental falldown one will not have the enthusiasm to go on to perfection. Lord Kṛṣṇa also states in the Bhagavad-gītā (9.30):

api cet su-durācāro
 bhajate mām ananya-bhāk
sādhur eva sa mantavyaḥ
 samyag vyavasito hi saḥ

“Even if one commits the most abominable actions, if he is engaged in devotional service, he is to be considered saintly because he is properly situated.” The most important point is that one should be properly engaged in the devotional service of the Lord, for then the Lord will excuse and purify an accidental falldown. One should, however, be most cautious to avoid such an unhappy event.