John Calvin Commentary Isaiah 29:19

"The meek also shall increase their joy in Jehovah, and the poor among men shall rejoice in the Holy One of Israel." — Isaiah 29:19 (ASV)

Then shall the humble again take joy in Jehovah. This is my translation of this passage, while others translate it, “They shall add,” or “continue to rejoice;” for the Prophet describes not a “joy” which is continued but rather a “joy” which is new. It is as if he had said, “Though they are now distressed and sorrowful, yet I will give them occasion for gladness, so that they will again be filled with “joy.”” He speaks of the “humble;” and from this it should be observed that our afflictions prepare us for receiving the grace of God, for the Lord casts us down and afflicts us, so that He may afterwards raise us up.

Thus, when the Lord corrects His people, we should not lose heart, but should recall those statements, so that we may always hope for better things, and may believe that, after such calamities and distresses, He will eventually bring joy to His Church. Yet we again learn from this what I briefly mentioned a little earlier: that the grace of illumination does not belong indiscriminately to all. For, although all have been chastened together, yet not all have had their hearts subdued by affliction, so as truly to become poor in spirit, or meek (Matthew 5:3, 5).