Jesus taught that prayer must be with forgiveness (Matthew 5:23, 24; 6:14-15; Mark 11:25-26) 

In these passages Jesus seems to be teaching us that if we have not forgiven someone we may as well not pray at all.  Mark 11:26 says, “If you do not forgive, neither will your Father in heaven forgive your trespasses.”

Jesus is not saying here that if you don’t forgive others you have lost your salvation; but He is saying that in your unwillingness to forgive someone you have cut off your fellowship with God.  Why?  Because in your sin against others (in not forgiving them) you sin against God too.  Sin always separates us from God, and so this is why when we sin He will not regard our prayers (Ps. 66:18, Jn. 9:31).

Now we know that there are many different kinds of sin, and all of them, if unconfessed will separate us…