John 8:31-47 (Evening Prayer)
"...and you will know the truth, and the truth will set you free.” John 8:31

This must be one of the more well-known slogans of Jesus which we can be sure has been applied in all sorts of situations. Understanding it in context may be helpful to better grasp its full import.
Firstly, that truth discernment comes to the one who abides in His word or teaching. The idea here is not so much knowledge or even meditation but someone who follows the teachings of Christ and walks in His way. We can consider a few examples:

If we walk in humility, we will be able to better discern truth.

If we walk in holiness and fear of God, we will be better able to discern the truth-consequences of wrong behaviour.

If we take daily worship and prayers seriously, we will have true wisdom to discern how to live.

The freedom experienced from knowing truth is opposed to a life bound to sin (John 8:34-36). Again here, Jesus teaches that to practise sin (deliberately living a life of sin) is to live without freedom for the person is being forced into a cycle of self-destruction or impoverishment. Jesus's answer to that is to ask us to follow His word. The point being made here is that Jesus wants us to live a life which is free to do what is right and in keeping with what is best for us and those around us.

This bondage also arises from following the will of the evil one (John 8:43,44) for to live a lie is to follow the father of lies (John 8:44). For a person who is not following Christ  will be "hard of hearing". He is unable to accept the truth or wisdom of the words of Christ as he is living in deception.

The heart of this passage, as we return to John 8:31, is about a hope and promise. Following Jesus leads us to truthful living, which in return sets us free to be the person we know we are destined to be.