Prominent prophets, teachers and characters of the Bible often use symbolisms when talking complex things. One of the more common pictures in Scripture is the idea of sowing and reaping. As an agriculture nation, Israel knows very well the difficulty in sowing and reaping. They are also aware of the rewards that the harvest brings.
In principle, the Bible also teaches the same thing not only for Christians but also unbelievers. The idea is simple: what you sow, you’d reap later and in bigger amounts. If you sow evil deeds, you will reap evil as well, and in bigger amounts. But if you sow goodness, you will reap more goodness in the future. This is the natural order of things.
However, God gives another factor in the equation – Himself. There is indeed the natural law of things, but God can still work through His grace and mercy to change the outcome, as long as the person gets reconciled with Him.