8 For the next words are, “They that sow in tears, shall reap in joy”. In this life, which is full of tears, let us sow. What shall we sow? Good works. Works of mercy are our seeds: of which seeds the Apostle says, “Let us not be weary in well doing; for in due season we shall reap if we faint not.” Speaking therefore of almsgiving itself, what says he? “This I say; he that sows sparingly, shall reap also sparingly.” He therefore who sows plentifully, shall reap plentifully: he who sows sparingly, shall reap also sparingly: and he that sows nothing, shall reap nothing.
Why do ye long for ample estates, where ye may sow plentifully? There is not a wider field on which you can sow than Christ, who has willed that we should sow in Himself. Your soil is the Church; sow as much as you can. But you have not enough to do this. Have you the will? As what you had would be nothing, if you had not a good will; so do not despond, because you have not, if you have a good will. For what do you sow? Mercy. And what will you reap? Peace. Said the Angels, Peace on earth unto rich men?
No, but, “Peace on earth unto men of a good will.” Zacchæus had a strong will, Zacchæus had great charity....Did then that widow who cast her two farthings into the treasury, sow little? Nay, as much as Zacchæus. For she had narrower means, but an equal will. She gave her two mites with as good a will as Zacchæus gave the half of his patrimony. If you consider what they gave, you will find their gifts different; if you look to the source, you will find them equal; she gave whatever she had, and he gave what he had....But if they are beggars whose profession is asking alms, in trouble they also have what to bestow upon one another.
God has not so forsaken them, but that they have wherein they may be tried by their bestowing of alms. This man cannot walk; he who can walk, lends his feet to the lame; he who sees, lends his eyes to the blind; and he who is young and sound, lends his strength to the old or the infirm, carries him: the one is poor, the other is rich.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)