1 Of what follows of the previous lesson, and has been read publicly to us today from the holy Gospel, I then deferred speaking, because I had already said much, and of that liberty into which the grace of the Saviour calls us it was needful to treat in no cursory or negligent way. Of this, by the Lord's help, we purpose speaking to you today. For those to whom the Lord Jesus Christ was speaking were Jews, in a large measure indeed His enemies, but also in some measure already become, and yet to be, His friends; for some He saw there, as we have already said, who should yet believe after His passion.
Looking to these, He had said, “When you have lifted up the Son of man, then shall you know that I am [He].” There also were those who, when He so spoke, straightway believed. To them He spoke what we have heard today: “Then said Jesus to those Jews who believed on Him, If you continue in my word, you shall be my disciples indeed.” By continuing you shall be so; for as now you are believers, by so continuing you shall be beholders. Hence there follows, “And you shall know the truth.”
The truth is unchangeable. The truth is bread, which refreshes our minds and fails not; changes the eater, and is not itself changed into the eater. The truth itself is the Word of God, God with God, the only-begotten Son. This Truth was for our sake clothed with flesh, that He might be born of the Virgin Mary, and the prophecy fulfilled, “Truth has sprung from the earth.” This Truth then, when speaking to the Jews, lay hid in the flesh. But He lay hid not in order to be denied, but to be deferred [in His manifestation]; to be deferred, in order to suffer in the flesh; and to suffer in the flesh, in order that flesh might be redeemed from sin.
And so our Lord Jesus Christ, standing full in sight as regards the infirmity of flesh, but hid as regards the majesty of Godhead, said to those who had believed on Him, when He so spoke, “If you continue in my word, you shall be my disciples indeed.” For he that endures to the end shall be saved. “And you shall know the truth,” which now is hid from you, and speaks to you. “And the truth shall free you.” This word, liberabit [shall free], the Lord has taken from libertas [freedom].
For liberat [frees, delivers] is properly nothing else but liberum facit [makes free]. As salvat [he saves] is nothing else but salvum facit [he makes safe]; as he heals is nothing else but he makes whole; he enriches is nothing else but he makes rich; so liberat [he frees] is nothing else but liberum facit [he makes free]. This is clearer in the Greek word. For in Latin usage we commonly say that a man is delivered (liberari), in regard not to liberty, but only to safety, just as one is said to be delivered from some infirmity.
So is it said customarily, but not properly. But the Lord made such use of this word in saying, “And the truth shall make you free (liberabit),” that in the Greek tongue no one could doubt that He spoke of freedom.
Source: Tractates on the Gospel of John (New Advent)