Mark 11:26 KJV
But if ye do not forgive, neither will your Father which is in heaven forgive your trespasses.
Mark 11:26, King James Version
In context
25 And when ye stand praying, forgive, if ye have ought against any: that your Father also which is in heaven may forgive you your trespasses.
26 But if ye do not forgive, neither will your Father which is in heaven forgive your trespasses.
27 And they come again to Jerusalem: and as he was walking in the temple, there come to him the chief priests, and the scribes, and the elders,