The meaning of the term "penal substitution" is that Jesus Christ’s sacrifice on the cross was on our behalf and for us. This article expains the meaning of the Greek word that is often translated as “for” in the English Bible, that it often stands for the idea of substitution.
This short article is an excerpt from John Piper's book The Future of Justification. It gives an exposition of our only great hope as Christians - that God is for us now and forever. This hope is founded on the obedience of Christ.