Here the apostle tacitly answers the common objection against liberal alms-giving; men are afraid they shall want themselves, what they give away to others. No, says the apostle, God is able to make all grace and mercy shown by you to abound the more towards you, that you, having a sufficiency of the comforts of this life, may abound in every good work of charity towards others.
As if he had said, Be not afraid to give, nor sparing in giving; for hereby you make God your debtor, and you will find him an all-sufficient paymaster; he will repay you both in temporals and spirituals. Thou shalt receive silver for thy brass, gold for thy silver, grace for thy gold, a treasure in haeven for thy dross on earth: nay, your gold and silver will multiply here, as seed sown when scattered with a wise and prudent hand."
The apostle here engages God's all-sufficiency for it; God will show his all-sufficiency, in giving you an all-sufficiency in all things; only we must remember, that we are to allow time; for Almighty God loves to be trusted upon his word: and those that will not give him credit, let them try if they can improve their estates better, or put them into safer hands.