John Calvin Commentary Romans 8:17

"and if children, then heirs; heirs of God, and joint-heirs with Christ; if so be that we suffer with [him], that we may be also glorified with [him]." — Romans 8:17 (ASV)

And if children, etc. By an argument taken from what is connected or what follows, he proves that our salvation consists in having God as our Father. It is for children that an inheritance is appointed; therefore, since God has adopted us as his children, he has at the same time ordained an inheritance for us.

He then indicates what sort of inheritance it is: that it is heavenly, and therefore incorruptible and eternal, such as Christ possesses. Christ's possession of it removes all uncertainty. Furthermore, it is a commendation of the excellence of this inheritance that we will partake of it in common with the only-begotten Son of God.

However, Paul's design, as will soon appear more fully, is to highly extol this inheritance promised to us, so that we may be contented with it, resolutely despise the allurements of the world, and patiently bear whatever troubles may press on us in this life.

If so be that we suffer together, etc. Various are the interpretations of this passage, but I approve of the following in preference to any other: “We are co-heirs with Christ, provided that, in entering on our inheritance, we follow him in the same way in which he has gone before.”

And Paul spoke of Christ in this way because he intended, through these steps, to transition to an encouraging theme: “God’s inheritance is ours because, by his grace, we have been adopted as his children. So that it may not be doubtful, its possession has already been conferred on Christ, whose partners we have become. But Christ came to it by the cross; therefore, we must come to it in the same manner.”

Nor should we dread what some fear—that Paul thus ascribes the cause of our eternal glory to our labours—for this way of speaking is not unusual in Scripture.

Paul indicates the order that the Lord follows in dispensing salvation to us, rather than the cause, for he has already sufficiently defended the free mercy of God against the merits of works. Now, in exhorting us to patience, he does not show from where salvation proceeds, but how God governs his people.