In order to establish the doctrine of penal substitution we are not dependent on a few isolated proof-texts here and there in Scripture. The doctrine is woven indelibly into the very fabric of the account of the crucifixion, with numerous threads drawn from the Old Testament. Rather than instinctively looking to the gospels to provide the facts about the crucifixion, and to the letters to supply the meaning of those facts, we must turn to the Old Testament as the vantage point from which we are to survey the cross. Antecedent Scripture provides us with all the categories we need to understand the cross.

Read the rest of this great article: The Condemned King: Mark 15 and the Doctrine of Penal Substitution – Reformation21.

Wish I had noticed this back when I was writing about propitiation!