“All flesh is grass!” Assyria was gone, and now Babylon was gone. Like the grass, nations and their leaders fulfill their purposes and then fade away, but the Word of God abides forever (Pss. 37:1–2; 90:1–6; 103:15–18; 1 Peter 1:24–25.)
To “bring good tidings” means “to preach the Good News.” The good news in that day was the defeat of Babylon and the release of the captive Jews (52:7–9). The Good News today is the defeat of sin and Satan by Jesus Christ and the salvation of all who will trust in Him (61:1–3; Luke 4:18–19). God’s arm is a mighty arm for winning the battle (Isa. 40:10), but it is also a loving arm for carrying His weary lambs (v. 11).
9 O Zion, that bringest good tidings, get thee up into the high mountain;
O Jerusalem, that bringest good tidings, lift up thy voice with strength;
Lift it up, be not afraid;
Say unto the cities of Judah, Behold your God!