John Trapp on Isaiah 31:4

Ver. 4. Like as the Lion, and the young Lion] That they may truſt in God, and not in the arm of fleſh, the Prophet ſetteth before them under two fit ſimilitudes the power of God, ver. 4. and the mercy of God, ver. 5. Theſe are the Jachin and the Boaz, the two main pillars and ſupports of Truſt in God. Procopius here noteth that the Lyon when he preyeth, firſt roareth ſo terribly, that he thereby amazeth both the cattle and their keepers, and then he falleth upon them and teareth them in pieces: ſo doth God firſt roar, that is, threaten by his Prophets, and then he deſtroyeth ſuch as obſtinate themſelves in a ſinful courſe.