Where does it say about if you cant forgive your brother how can god forgive you?

Clearly, forgiveness is a key concept in scripture. God is the only one who can forgive sin, as least to the point of freeing one from the penalty of sin. God does encourage us to forgive one another. One of the disciples asked how many times one should forgive another, 7 times? To which Jesus replied 7 times 7 (or 70 times 7), in order to make the point that there should be no end to forgiveness. It usually follows that those who have a deep understanding of the wretchedness of sin, and the extent to which God went to forgive us (Christ's death on the cross), these folks are usually those with forgiving hearts. On the other hand, those with a shallow understanding of the depths from which they've been forgiven can easily neglect or refuse to forgive others. Jesus even told a parable about forgiveness. The bottom line was that folks who do not forgive others are probably not in a position to be gaining forgiveness from God. Apart from the forgiveness associated with salvation, there's also forgiveness involving our relationship with God. If we sin as believers we are to confess our sin (to God) and He forgives based on the blood of Christ. Even as believers who are forgiven, our closeness to God can be marred by sin. This is the remedy by which we can regain that closeness. God expects us to be no less forgiving with our brothers and sisters in Christ. Do we "have to forgive?" I don't know, but I do know that one who refuses to forgive probably has little to no understanding of the depravity of sin and the lengths to which God went to provide his/her forgiveness. Such a believer will have severe dealings with God.