Charles Williams has said of the Lord's Prayer, "No word in English carries a greater possibility of terror than the little word 'as' in that clause." What makes the 'as' so terrifying? The fact that Jesus plainly links our forgiven-ness by the Father with our forgiving-ness of fellow human beings. Jesus' next remark could not be more explicit: 'If you do not forgive men their sins, your Father will not forgive your sins.'
Philip Yancey (1997). “What's So Amazing about Grace?”, p.87, Harper Collins