Radak

The meek shall eat and be satisfied: They shall praise the Lord that seek after Him: – i.e. Israel, because they are meek, for the Gentiles have been proud until the time of the redemption of Israel; so also Israel is identical with those that seek after Him, for they are seeking after Him in the exile; and when they are redeemed they shall eat and be satisfied with the spoil of their enemies, and delight themselves – the reverse of what they experienced in exile – and they shall say to them: Let your heart live: – the interpretation of which is on the lines of, “and the spirit of Jacob lived” (ibid. 45:27), the converse of “and his heart died” (1 Sam. 25:37); for the living spirit is in the heart, and when man is in trouble his heart dies, as he (the Psalmist) says (Ps. 109:22), and when he passes out from trouble to relief, behold, his heart lives. And the significance of for ever (is): – they shall be no longer in exile, but shall be in their own land, rejoicing and glad of heart, they and their children, for ever.