John Calvin Commentary Acts 10:42

"And he charged us to preach unto the people, and to testify that this is he who is ordained of God [to be] the Judge of the living and the dead." — Acts 10:42 (ASV)

And he commanded us. He begins in this place to treat of the kingdom of Christ when he says that Christ rose again for this reason: that he might one day judge the world. For by the same right, the government of heaven and earth, and the perpetual government of the Church, are due to him.

He says that he will be judge of quick and dead; because, when the dead will rise again, others also, who will then remain alive, will be changed in a moment, as Paul teaches in the fifteenth chapter of the First Epistle to the Corinthians (1 Corinthians 15:51–52) and in the fourth chapter of the First Epistle to the Thessalonians (1 Thessalonians 4:17). In the word testify there is great weight, because, as men are naturally inclined to unbelief, the simple preaching of the gospel would not be so effective unless the Lord establishes it with strong protestations.

And chiefly, every one of us feels acutely in himself how hard it is both to lift up our minds, which are entangled in earthly snares, to hope for the coming of Christ, and also continually to keep them fixed in this meditation, since, in their fickleness, they are unceasingly carried here and there.