Complete Commentary on the Whole Bible, by Matthew Henry, at sacred-texts.com
(Psa 126:1-3) Those returned out of captivity are to be thankful.
(Psa 126:4-6) Those yet in captivity are encouraged.
It is good to observe how God's deliverances of the church are for us, that we may rejoice in them. And how ought redemption from the wrath to come, from the power of sin and of Satan, to be valued! The sinner convinced of his guilt and danger, when by looking to a crucified Saviour he receives peace to his conscience, and power to break off his sins, often can scarcely believe that the prospect which opens to him is a reality.
The beginnings of mercies encourage us to pray for the completion of them. And while we are in this world there will be matter for prayer, even when we are most furnished with matter for praise. Suffering saints are often in tears; they share the calamities of human life, and commonly have a greater share than others. But they sow in tears; they do the duty of an afflicted state. Weeping must not hinder sowing; we must get good from times of affliction. And they that sow, in the tears of godly sorrow, to the Spirit, shall of the Spirit reap life everlasting; and that will be a joyful harvest indeed. Blessed are those that mourn, for they shall be for ever comforted. When we mourn for our sins, or suffer for Christ's sake, we are sowing in tears, to reap in joy. And remember that God is not mocked; for whatever a man soweth that shall he reap, Gal 6:7-9. Here, O disciple of Jesus, behold an emblem of thy present labour and future reward; the day is coming when thou shalt reap in joy, plentiful shall be thy harvest, and great shall be thy joy in the Lord.