If one believes the sermon on the mount is doctrine for the body of Christ, then one must conclude that forgiveness is conditional on forgiving others. This would be a work of obedience.
14 For if ye forgive men their trespasses, your heavenly Father will also forgive you:
15 But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.
I do not believe the sermon on the mount is Christian doctrine but rather doctrine for the Jew living in the millennium kingdom on earth where Christ will reign on the throne of David. The sermon on the mount is a kind of constitutional guide to living in this kingdom.
The sermon on the mount was Jesus raising the bar of the Law for a number of reasons..
1) Because the people had come to the conclusion that Keeping the Law was the key to justifying their own entry into Gods Eternal kingdom.. That they could succeed in doing the Law as it was written..
The fact was that no one succeed in doing the written law without failure but some people deluded themselves into believing that they had.. Remember the young man who came to Jesus asking what good thing he could do to enter into Gods kingdom? When Jesus said keep the laws the young man said he had done so from his childhood. Now the young guy may have honestly believed he had kept all the laws without fail so Jesus then told him to go sell all his possessions and give them to the poor and come follow Me.. If you want to
be perfect and that's the critical words in that passage a person must be perfect to justly enter into Gods kingdom.. Something that Jesus later in that passage said it is impossible for a man but with God all things are possible.. Meaning a man cannot justify himself by the LAW But the LORD Jesus can justify a man because of what He was going to do on the cross..
2) So in the sermon on the mount Jesus message would convince anyone standing and listening to it that they where doomed to fail to live up to those standards.. That they would have to be a perfect person to succed in living up to those standards.. As the Bible says the Law condemns everyone under the Law because it reveals that all are guilty and unworthy of eternity with God.. The Laws job is to show to us just how impossible it is for us to justify ourselves before God..
Galatians 3: KJV
21 "Is the law then against the promises of God? God forbid: for
if there had been a law given which could have given life, verily righteousness should have been by the law. {22} But
the scripture hath concluded all under sin, that the promise
by faith of Jesus Christ might be given to
them that believe. {23} But before faith came, we were kept under the law, shut up unto the faith which should afterwards be revealed. {24} Wherefore
the law was our schoolmaster to bring us unto Christ, that we might be
justified by faith."
The Law condemned us and was our schoolmaster making it clear to us that we could never be justified by law doing.. So when the the Way of salvation by belief in the Atonement of Jesus came,, the Law made it clear to us that the Way of the Gospel was the only way..
3) Some Jews in the times of Jesus because they where certain that doing the Law was the only way to justify themselves, well they had convinced themselves that they could and where doing the Law and so Jesus revealed His teachings on the mount to make it clear to those assembled just how short they where falling from the standard.. Of course a lot of Jews hated Jesus for this.. There are many people today who believe in the Works salvation doctrine who likewise believe they are succeding in doing the Law and come online here and preach their perfection in the flesh doctrine, deluding themselves and attempting to undermine the Faith babes in Christ have in the Atonement of Jesus to save them..
So we come to the teaching of Jesus on the sermon on the mount about forgiving others..
14 For if ye forgive men their trespasses, your heavenly Father will also forgive you:
15 But if ye forgive not men their trespasses, neither will your Father forgive your trespasses.
So is this teaching good and true for those who where listening to it the Jews under the law? Yes
Is it still good and should we strive to forgive without failure all who have done us wrong? Yes
Did the Jews in the audience or us here today do this teaching without fault? No
So what do we have and what was later provided for the Jews in the audience who heard this teaching of Jesus? How could there transgression and our transgression against this teaching be forgiven?
The Atonement of the LORD Jesus Christ.. That covers us for our transgressions against His will...