Packer Quote on Penal Substitution

I want to remember this quote from J.I. Packer

"Jesus Christ our Lord, moved by a love that was determined to do everything necessary to save us, endured and exhausted the destructive divine judgment for which we were otherwise inescapably destined, and so won us forgiveness, adoption and glory. To affirm penal substitution is to say that believers are in debt to Christ specifically for this, and that this is the mainspring of all their joy, peace and praise both now and for eternity."