By the Spirit; by a resolution from the Spirit, as one of his gifts, and not by judicial astrology, or any other means real or pretended; for it is a prerogative of God only to foretell things to come, as Isaiah 41:22,23. Which came to pass in the days of Claudius Caesar: this famine Suetonius and other heathen writers make mention of, though some place it in one year, and some in another year, of Claudius's reign. It may be there were divers famines, or one might continue divers years; but thus God, who provided for the patriarchs by means of Joseph's foreseeing of the scarcity in Egypt and elsewhere, provides for his church now also by a like prediction. God's omniscience is exerted for his church's preservation.
Related Commentaries of Acts 11:28
Acts 11:28
28 And there stood up one of them named Agabus, and signified by the Spirit that there should be great dearth throughout all the world: which came to pass in the days of Claudius Caesar.