A.T. Robertson Commentary Mark 11:25

"And whensoever ye stand praying, forgive, if ye have aught against any one; that your Father also who is in heaven may forgive you your trespasses." — Mark 11:25 (ASV)

Whensoever ye stand (οταν στηκετε). Late form of present indicative στηκω, from perfect stem εστηκα. In LXX. Note use of οταν as in 11:19. Jesus does not mean by the use of "stand" here to teach that this is the only proper attitude in prayer.

That your Father also may forgive you (ινα κα ο πατηρ αφη υμιν). Evidently God's willingness to forgive is limited by our willingness to forgive others. This is a solemn thought for all who pray. Recall the words of Jesus in Mt 6:12,14f.