2 Timothy 1:8

Be not then therefore ashamed of the testimony of our Lord,
&c.] Either that testimony which Christ bore personally by his doctrine and miracles, and by his sufferings and death; or rather the Gospel so called, because it comes from Christ, and because it is a testimony concerning him; concerning his person, his offices, his righteousness, blood, sacrifice, and satisfaction; concerning his obedience, sufferings, death, resurrection, ascension, session at God's right hand, intercession for his people, and second coming to judgment; and concerning life and salvation by him: and which no preacher or professor of Christ has reason to be ashamed of, it being so true in itself, so great, so glorious, and so useful; and whoever is, Christ will be ashamed of him another day:

nor of me his prisoner;
for Paul was now a prisoner at Rome, but not for any capital crime, or for any immorality, but for the sake of Christ, and for preaching his Gospel; wherefore none of his friends had any reason to be ashamed of him; he was suffering in a glorious cause, and setting a noble example to others; it looks as if Timothy was somewhat blameworthy in this respect.

But be thou partaker of the afflictions of the Gospel;
the Gospel is here represented as a person suffering afflictions, and the apostle would have Timothy suffer them as that did, and along with it; he means those afflictions which come upon men for preaching and professing the Gospel; for though the Gospel is a Gospel of peace, yet, through the corruption and depravity of men, it brings a sword, division, and trouble. Tribulation arises on account of it; and this should be endured patiently, and constantly, for the sake of it:

according to the power of God;
which is only sufficient to enable persons to bear them; and is mentioned for the encouragement of Timothy and others, to endure them cheerfully.