“Much people of the Jews therefore knew that he was there: and they came not for Jesus’ sake only, but that they might see Lazarus also, whom he had raised from the dead. But the chief priests consulted that they might put Lazarus also to death. Because that by reason of him many of the Jews went away, and believed on Jesus." (New Testament, John, Chapter 12 9-11)
There are no recorded words of Lazarus in the Gospels. And yet, because of him, many people believed in Jesus. They heard what happened, that Lazarus was dead, in the tomb for four days, and then he was alive because of Jesus.
Jesus did not really ever tell us to DO our witnessing. Rather, we are to BE a witness of His love, His healing power, His ability to take a life that is spiritually dead and make us alive. And even if it's a case where words are spoken, they are simple to their core, like: "Come and see". Scriptures teach we are to "abide" in Him. These all suggest a state of being. Our very being can be a witness of the reality and goodness of our God.
I think of the words credited to both Mother Teresa and Francis of Assisi: “Witness all the time and when necessary use words.”