In the context of these verses, Jesus has just talked about how his opponents will know he is from God after they crucify him, after they "have lifted up the Son of Man." In John 3:14, Jesus is lifted up like the snake Moses lifted up in the desert to heal Israel.
To be freed implies that you were not free before, and Jesus’ opponents resist his teaching that he will free them. They are the children of Abraham. They have never been slaves. Of course this claim in itself is not really true. Israel had repeatedly been enslaved over the centuries to various foreign powers, and they were under the thumb of the Romans at the time of Jesus. By the time of John they had destroyed Jerusalem—an irony that would not have escaped John’s audience. But the slavery Jesus has in mind is not physical slavery, but a slavery to sin, which is a failure to love one another (1 John 4:7-8). A slave is not yet a son.
The truth about Jesus sets people free. What is that truth? Certainly trusting in Jesus as Messiah brings eternal life (John 3:16; 20:31) and includes his atoning death, the bread and wine that gives life. Another truth is that Jesus authentically represented God the Father. To be a follower of Jesus is to follow his teaching, which is to follow the teaching of God the Father. But what is that teaching? What does it mean to be free from sin? Surely at least in part it means to be freed to love each other, to show love to each other. How hard it is to love others in our own power. How much freer the world would be if everyone showed love to each other.
Truth sets a person free to be sure. Such freedom is not always as comfortable as we dreamt it would be. Sometimes it is more comfortable to have the decisions made for us or not to know other possibilities. We may not want to know truths that are inconvenient to our current way of life. Truth can bring conflict, and truth can force change. We may not want to know about the person near us who needs help, because then we need to do something. We may not want to know whether we have cancer or whether our current way of living will likely lead toward future crises—including eternal judgment. But the truth now makes it more likely that we will avert future catastrophes.
Father, as hard as the truth and the right may be, give us an unswerving commitment to it and to obey you no matter how uncomfortable the immediate consequences.
"I believe that unarmed truth and unconditional love will have the final word in reality. This is why right, temporarily defeated, is stronger than evil triumphant." Martin Luther King Jr.