Jeremiah 1:9 - Ellicott's Commentary On The Whole Bible

The Lord put forth his hand... — The symbolic act seems to imply something like a waking vision, like that of Isaiah (Isaiah 6:6), and the act itself reminds us of the “live coal” laid upon the prophet’s mouth, as there recorded. The “hand of the Lord,” as in Ezekiel 3:14; Ezekiel 8:1., and elsewhere, was the received symbol of the special influence of the Spirit of the Lord; and here, as in the case of Isaiah, the act implied the gift of new powers of thought and utterance. The words which a prophet speaks, like those which were to be spoken by the Apostles of Christ (Matthew 10:20), are not his own words, but those put into his heart by the Spirit of the Father. So “the finger of God” in Luke 11:20 answers to “the Spirit of God” in Matthew 12:28.