Hermas (9.3.2-9.3.6)

He said to me, You have heard correctly, for that is so. For he who has received remission of sin ought never to sin again, but to live in purity.

But since you ask accurately concerning all things, I will explain this also to you without giving an excuse to those who in the future shall believe or to

For those, then, who were called before these days, did the Lord appoint repentance, for the Lord knows the heart, and knowing all things beforehand he knew the weakness of man and the subtlety of the devil, that he will do some evil to the servants of God, and will do them mischief.

The Lord, therefore, being merciful, had mercy on his creation, and established this repentance, and to me was the control of this repentance given.

But I tell you, said he, after that great and holy calling, if a man be tempted by the devil and sin, he has one repentance, but if he sin and repent repeatedly it is unprofitable for such a man, for scarcely shall he live.