Adams on Psalm 126:5

5 They that sow in tears shall reap in joy
They sow in faith
and God will bless that seed: it shall grow up to heaven, for it is sown in the side of Jesus Christ who is in heaven. "He that believeth on God", this is the seed; "shall have everlasting life" (Joh 5:24); this is the harvest. Qui credit quod non videt, videbit quod credit, —he that believes what he doth not see; this is the seed: shall one day see what he hath believed; this is the harvest. They sow in obedience
this is also a blessed seed, that will not fail to prosper Wheresoever it is cast. "If ye keep my commandments"; this is the seed: "ye shall abide in my love" (Joh 15:10); this is the harvest. (Ro 6:22), "Ye are become servants to God, and have your fruit unto holiness"; this is the sowing: "and the end everlasting life"; this is the reaping. Obedientia in tetris, regnabit in coelis,—he that serves God on earth, and sows the seed of obedience, shall in heaven reap the harvest of a kingdom. They sow in repentance
and this seed must needs grow up to blessedness ... Many saints have now reaped their crop in heaven, that sowed their seed in tears. David, Mary Magdalene, Peter: as if they had made good the proverb, "No coming to heaven with dry eyes." Thus nature and God differ in their proceedings. To have a good crop on earth, we desire a fair seedtime; but here a wet time of sowing shall bring the best harvest in the barn of heaven. "Blessed are they that mourn"; this is the seeding: "for they shall be comforted" (Mt 5:4); this is the harvest. They sow in renouncing the world, and adherence to Christ
and they reap a great harvest. "Behold", saith Peter to Christ, "we have forsaken all, and followed thee" (Mt 19:27); this is the seeding. "What shall we have therefore?" What? "You shall sit on twelve thrones, judging the twelve tribes of Israel" (Mt 19:28-29); all that you have lost shall be centupled to you: "and you shall inherit everlasting life"; this is the harvest. "Sow to yourselves in righteousness, and reap in mercy": Ho 10:12. They sow in charity
He that sows this seed shall be sure of a plentiful crop. "Whosoever shall give to drink to one of these little ones a cup of cold water only"—a little refreshing—"in the name of a disciple; verily I say unto you, he shall in no wise lose his reward": Mt 10:42. But if he that giveth a little shall be thus recompensed, then "he that soweth bountifully shall reap bountifully": 2 Cor 9:6. Therefore sparse abroad with a full hand, like a seeds man in a broad field, without fear. Doth any think he shall lose by his charity? No worldling, when he sows his seed, thinks he shall lose his seed; he hopes for increase at harvest. Do you dare trust the ground and not God? Sure God is a better paymaster than the earth: grace doth give a larger recompense than nature. Below thou mayest receive forty grains for one; but in heaven, (by the promise of Christ,)a hundred fold: a "measure heapen, and shaken, and thrust together, and yet running over." "Blessed is he that considereth the poor"; this is the seeding: "the Lord shall deliver him in the time of trouble" (Ps 41:1); this is the harvest.
As quoted in Spurgeon's Treasury of David