Elsewhere in Scripture the Lord has used the comparison of a lion’s roar to indicate that he (through his prophets) was announcing mighty works he was about to do (see Jeremiah 25:30; Hosea 11:10; Joel 3:16; Amos 1:2; Amos 3:8). Those mighty works are characteristically calamitous for God’s enemies and redemptive for God’s people.
3 and called out with a loud voice, like a lion roaring. When he called out, the seven thunders sounded.