Summary: Paul quotes a proverb that is instructive for believers as they bring their gifts before the Lord.
“Whoever sows sparingly will also reap sparingly, and whoever sows bountifully will also reap bountifully. Each one must give as he has decided in his heart, not reluctantly or under compulsion, for God loves a cheerful giver.” 
“Whoever sows sparingly will also reap sparingly, and whoever sows bountifully will also reap bountifully.” Every language has proverbs peculiar to that particular language. English is an expressive and marvellously powerful language in part because it is so dynamic, adapting to the changing world including the adoption of sayings, proverbs and adages found in other languages. The proverb Paul quotes is obviously ancient; and though we cannot speak with authority of the origin of the proverb it was certainly current among those conversant with the lingua franca of the New Testament world—the language we now know as Koine Greek. I suspect that the proverb quoted is as ancient, in one form or another, as agrarian society. Clearly, the proverb has its roots in the soil. So long as man has tilled the soil, I would suppose that similar proverbs have been quoted.
At the outset of the message, I need to be very clear concerning my horticultural abilities. I make no claim to being a horticulturist; my thumb is not green; plants surrender to the inevitable when entrusted to my care. Therefore, I offer no advice concerning your efforts to plant or to grow plants in your yards. However, Paul is not speaking of plants in this proverb. He is applying the universal truth underlying the proverb to instruct his readers in a biblical principle concerning giving. The greater your gift, the greater the return you may anticipate. Though there may be caveats applied to the proverb, the truth remains that generosity begets blessing. Join me in a study of this ancient proverb to discover how the truth may be applied in contemporary life.
THE BIBLICAL BASIS FOR GENEROSITY IN GIVING — “Whoever sows sparingly will also reap sparingly, and whoever sows bountifully will also reap bountifully” [2 CORINTHIANS 9:6]. Paul writes with broad strokes at this point. This is not, as many holding to charismatic concepts imagine, a blank cheque with which to enrich oneself. This is not, as one prominent religious huckster was wont to say, a statement concerning “seed money.” This is a general, spiritual precept given to the people of God. It is worthy of study if for no other reason than to instruct us in actions that are pleasing to God.
The proverb speaks of truth that is witnessed elsewhere in Scripture, especially from the Proverbs. Consider several Proverbs that speak of the blessing attending generosity.
“Honour the LORD with your wealth
and with the firstfruits of all your produce;
then your barns will be filled with plenty,
and your vats will be bursting with wine.”
[PROVERBS 3:9, 10]
The principle enunciates a general precept that the individual who sees wealth as entrusted by God will seek to honour God; in turn, that one will be entrusted with even greater wealth.