You may be asking, "If I sow by giving, what's the harvest? How will I recognize any results?"
That is a smart, thoughtful question! What is the point of giving your money or time if you can't see, or recognize the results? Let me show you some harvests you could be getting.
In my favourite Bible chapter it says, "This service you perform is not only supplying the needs of God's people but is also overflowing in many expressions of thanks to God. Because of the service by which you have proved yourselves, men will praise God for the obedience that accompanies your confession of the gospel of Christ, and for your generosity in sharing with them and with everyone else. And in their prayers for you their hearts will go out to you, because of the surpassing grace God has given you. Thanks be to God for his indescribable gift! 2 Cor. 9:12-15.
In this example, the seed sown is your service to supply the needs of God's people. The resulting harvest is the thanksgiving to God, and their heart-felt prayers for you! Do you know the value of having others praise God for you when they pray, and asking God's blessings on you? That is priceless.
Another example, if you give tithes regularly to your church, it will be able to grow and function well. You'll be able to keep a good pastor instead of having to make do with rotating volunteers. (Or to be closed down).
Because you pledge to support a missionary regularly, even with a small gift every month, they are able to devote their time and skills to learning another language and culture and bring the gospel to people who might never know of it otherwise.
In yet another instance, you might send money to a disaster area like Haiti after their earthquake. Many are fed and lives saved, and some souls saved for eternity too. They are grateful, and though they are unlikely to ever be able to return a gift to you, the fact that they are precious in God's sight can be a sufficient reward for you.
Note that God's Word promises, "He who is kind to the poor lends to the LORD, and He will reward him for what he has done." (Proverbs 19:17niv). God will never remain in debt to us for helping the poor.
He warns also, "Do not exploit the poor because they are poor and do not crush the needy in court, for the LORD will take up their case and will plunder those who plunder them." (Proverbs 22:22 niv). We quarrel with the Almighty God Himself, if we try to take advantage of the poor and needy!.
One more example of Sow by giving, what's the harvest?
Let's say you know some Christian missionary family, and they are in a crisis, needing funds to get to their ministry, or past a difficult time. If you help them out with a financial gift and a card of encouragement, they will become your loyal, devoted friends and pray for you and thank God for you often. You may never know this side of Heaven how much more they have contributed to your life than you did to theirs.
We can project ourselves into more situations like these. Please do. But always recognize that we while we are sowing by giving, what IS the harvest; God is glorified, and people He loves - even if they are strangers to us - are blessed and helped in His name. When that happens God sees that as a gift to Him, or His Son, Jesus, and He will never remain indebted to us. He will out-give us all the time.
What God gives us is not necessarily in the same currency as we gave to Him. Money is an earthly economy which God does use, but He also trades in spiritual blessings, protection from evil, powerful prayers that transform lives, and many more blessings. Good friends and a loving family come from God too! Health as well, and even business success. Do not limit God. Expand your view to see His bigger scope and to appreciate the treasures He gives you!
I can personally testify to both sides of this - the receiving and the giving. I have received gifts from people that HAD to be directed by the Lord, (and I still pray for them years later!) I am beginning to be in a better position to give to others now, and find that the more I gladly give, the more the Lord seems to provide over time. Now I know when I sow by giving, what's the harvest! It's worth it!