I find two good messages in this group of verses. First the message that God won’t be fooled by people who act good while doing bad; they will reap what they sow. And the second related message that we must not give up and become weary of doing good.
Do not be deceived: God cannot be mocked. A man reaps what he sows. The one who sows to please his sinful nature, from that nature will reap destruction; the one who sows to please the Spirit, from the Spirit will reap eternal life. Let us not become weary in doing good, for at the proper time we will reap a harvest if we do not give up. Therefore, as we have opportunity, let us do good to all people, especially to those who belong to the family of believers.