John Calvin Commentary Hebrews 13:20

"Now the God of peace, who brought again from the dead the great shepherd of the sheep with the blood of an eternal covenant, [even] our Lord Jesus," — Hebrews 13:20 (ASV)

Now the God of peace, etc. To make his prayer align with what he desired them to do, he ends his Epistle with prayer; and he asks God to confirm, or to fit, or to perfect them in every good work; for such is the meaning of καταρτίσαι. Therefore, we conclude that we are by no means fit to do good until we are made or formed for this purpose by God, and that we will not continue long in doing good unless he strengthens us, for perseverance is his special gift. There is no doubt that since, as it seems, gifts of the Spirit that were not ordinary had already appeared in them, what is prayed for is not the initial work with which they began, but the polishing by which they were to be made perfect.

That brought again from the dead, etc. This clause was added for confirmation, for he suggests that we only pray to God rightly for him to lead us to perfection when we acknowledge his power in Christ’s resurrection and acknowledge Christ himself as our pastor. In short, he wants us to look to Christ so that we may rightly trust in God for help; for Christ was raised from death for this purpose: that we might be renewed to eternal life by the same power of God; and he is the great pastor of all, so that we may protect the sheep committed to him by the Father.

Through the blood, etc. I have translated it as “In the blood,” because just as ב, meaning “in,” is often taken in the sense of with, I prefer that interpretation here. For it seems to me that the Apostle means that Christ rose from the dead in such a way that his death was not abolished, but retains its efficacy forever. It is as if he had said, “God raised up his own Son, but in such a way that the blood he shed once for all in his death remains efficacious after his resurrection for the ratification of the everlasting covenant, and produces fruit as if it were continually flowing.”