Amos 3:8

The lion hath roared - God hath sent forth a terrible alarm, Who will not fear? Can any hear such denunciations of Divine wrath and not tremble?

The Lord God hath spoken - And those only who are in communion with him have heard the speech. Who can but prophesy? Who can help proclaiming at large the judgment threatened against the nation?

But I think נבא naba, here, is to be taken in its natural and ideal signification, to pray, supplicate, or deprecate vengeance. The Lord hath spoken of punishment - who can help supplicating his mercy, that his judgments may be averted?

The Lion hath roared: who will not fear? The Lord God hath spoken: who can but prophesy? - that is, there is cause for you to fear, when the Lord "roareth from Zion;" but if ye fear not, God's prophets dare not but fear. So Paul saith, "necessity is laid upon me; yea, woe is unto me if I preach not the Gospel! For if I do this thing willingly, I have a reward; but if against my will, a dispensation" of the Gospel "is committed unto me" 1 Corinthians 9:16-17; and Peter and John, "whether it be right in the sight of God to hearken unto you more than unto God, judge ye! For we cannot but speak the things which we have seen and heard" Acts 4:19-20; Moses was not excused, though slow of speech; nor Isaiah, though of polluted lips; nor Jeremiah, because he was a child; but God said, "Say not, I am child, for thou shalt go to all that I shall send thee, and whatsoever I command thee, thou shalt speak" Jeremiah 1:7. And Ezekiel was bidden, "be not rebellious, like that rebellious house" Ezekiel 2:8. And when Jeremiah would keep silence, he saith, "His Word was in mine heart as a burning fire, shut up in my bones, and I was weary with forbearing and I could not stay" Jeremiah 20:9.

3:8 Hath roared - As a lion roareth when near his prey: so God hath terribly threatened what is near to be done. Prophesy - Amos can not but speak what he had heard.