My uncle Loy Mitchell died in June 2015. I remember him quoting this verse to me. He was a seed sower. I remember riding in the truck with him in Zimbabwe, and he would throw out tracts about Jesus along the way to preach. He preached on his way to preach. People along the road, hungry for reading material, hungry for truth, ran to pick up the tracts.
Loy quoted the above Isaiah text to me, and it has always been a meaningful text to me, particularly when I forget that my life work is not about what I can see produced but about planting seeds that build for the kingdom of God. The kingdom of God, Jesus often said, is like a tiny seed that is planted and it grows to be a huge tree.
Yahweh, help me to trust your word does not return to you empty or void. It will do what you sent it out to do. Help me to preach your word faithfully, to plant seeds of your goodness and love, and watch what you do.
An old missionary in India once said, "Don't bring the gospel as a potted plant, but take it as seed and plant it in the soil, and then it will grow there in the way God sees fit." Fast from thinking you have to package up stuff for people, and plant seeds.
When you become worried about your influence, remember, even memorize this text. Give something to the poor or the poor in spirit, and don't worry about what God will do with it. His word, your actions done in the Spirit of Christ, will not come back empty.