Albert Barnes on Romans 6:8

Now if we be dead with Christ. If we be dead in a manner similar to what he was; if we are made dead to sin by his work, as he was dead in the grave. Rom 6:4.

We believe. All Christians. It is an article of our faith. This does not refer to the future world so much as to the present. It becomes an article of our belief that we are to live with Christ.

That we shall also live with him. This does not refer primarily to the resurrection, and to the future state, but to the present. We hold it as an article of our faith, that we shall be alive with Christ. As he was raised up from death, so we shall be raised from the death of sin. As he lives, so we shall live in holiness. We are in fact raised up here, and, as it were, made alive to him. This is not confined, however, to the present life; but as Christ lives for ever, so the apostle goes on to show that we shall.