Matthew 18

To his disciples that Lord taught two principles that at first may seem a little bit at odds with each other -

"...if thy hand or thy foot offend thee, cut them off, and cast them from thee: it is better for thee to enter into life halt or maimed, rather than having two hands or two feet to be cast into everlasting fire.
9 And if thine eye offend thee, pluck it out, and cast it from thee: it is better for thee to enter into life with one eye, rather than having two eyes to be cast into hell fire." (New Testament | Matthew 18:8 - 9)

And -

"...Lord, how oft shall my brother sin against me, and I forgive him? till seven times?
22 Jesus saith unto him, I say not unto thee, Until seven times: but, Until seventy times seven." (New Testament | Matthew 18:21 - 22)

One response seems to be to the individual or in our personal relationships. The Lord later taught -

"I, the Lord, will forgive whom I will forgive, but of you it is required to forgive all men." (Doctrine and Covenants | Section 64:10)

But the other seemed to be a response to the disciples in the administration of the Church. The Lord also taught his priesthood leaders -

"...him that repenteth not of his sins, and confesseth them not, ye shall bring before the church, and do with him as the scripture saith unto you, either by commandment or by revelation.
13 And this ye shall do that God may be glorified—not because ye forgive not, having not compassion, but that ye may be justified in the eyes of the law, that ye may not offend him who is your lawgiver—
14 Verily I say, for this cause ye shall do these things." (Doctrine and Covenants | Section 64:12 - 14)

I believe this is what the Savior was referring to using the analogy of the body for the Church. Bruce R. McConkie wrote -

"Iniquity within the Church and kingdom of God on earth cannot be condoned; unrepentant members of the Church must be cast out, even though their severance from the body of the saints is as grievous an operation as cutting off a hand or foot or plucking out an eye. False doctrines and evil practices originating with those outside the Church are easily identified, both because of their nature and their source. But the same doctrines and practices when espoused and promulgated by those within the fold of Christ, who are presumed to be in harmony with the truth, may more easily lead the unwary astray. Indeed, one of the major factors contributing to the great apostasy in the early part of the Christian Era was the failure to cut off the dead, decaying, and corrupt branches of the gospel tree. (DNTC 1:419)