5 But observe whether that was fulfilled in his case which the Psalm now speaks of. “The Lord strengthens the righteous.— Not only so” (says that same Paul, while suffering many evils), “but we glory in tribulations also: knowing that tribulation works patience, and patience experience; and experience hope; but hope makes not ashamed, because the love of God is shed abroad in our hearts by the Holy Ghost, which is given unto us.” Justly is it said by him, now righteous, now “strengthened.” As therefore those who persecuted him did no harm to him, when now “strengthened,” so neither did he himself do any harm to those whom he persecuted. “But the Lord,” he says, “strengthens the righteous.”...
Source: The Enarrations, or Expositions, on the Psalms (New Advent)