I don't know if people are aware of it but Jerome's 'citation' of the Gospel of the Hebrews is more nuanced than a 'citation.' It appears in a fictitious dialogue which Jerome penned:
1. Critob. I am charmed with the exuberance of your eloquence, but at the same time I would remind you that, Proverbs 10:19 In the multitude of words there wants not transgression. And how does it bear upon the question before us? You will surely admit that those who have received Christian baptism are without sin. And that being free from sin they are righteous. And that once they are righteous, they can, if they take care, preserve their righteousness, and so through life avoid all sin.
Attic. Do you not blush to follow the opinion of Jovinian, which has been exploded and condemned? For he relies upon just the same proofs and arguments as you do; nay, rather, you are all eagerness for his inventions, and desire to preach in the East what was formerly condemned at Rome, and not long ago in Africa. Read then the reply which was given to him, and you will there find the answer to yourself. For in the discussion of doctrines and disputed points, we must have regard not to persons but to things. And yet let me tell you that baptism condones past offenses, and does not preserve righteousness in the time to come; the keeping of that is dependent on toil and industry, as well as earnestness, and above all on the mercy of God. It is ours to ask, to Him it belongs to bestow what we ask; ours to begin, His it is to finish; ours to offer what we can, His to fulfil what we cannot perform. For except the Lord build the house, they labour in vain that build it. Except the Lord keep the city, the watchman wakes but in vain. Wherefore the Apostle 1 Corinthians 9:24 bids us so run that we may attain. All indeed run, but one receives the crown. And in the Psalm it is written, O Lord, you have crowned us with your favour as with a shield. For our victory is won and the crown of our victory is gained by His protection and through His shield; and here we run that hereafter we may attain; there he shall receive the crown who in this world has proved the conqueror. And when we have been baptized we are told, John 5:14 Behold you are made whole; sin no more lest a worse thing happen unto you. And again, 1 Corinthians 3:16-17 Do you not know that you are a temple of God, and that the Spirit of God dwells in you? If any man profane the temple of God, him shall God destroy. And in another place, 2 Chronicles 15:2 The Lord is with you so long as you are with Him: if you forsake Him, He will also forsake you. Where is the man, do you suppose, in whom as in a shrine and sanctuary the purity of Christ is permanent, and in whose case the serenity of the temple is saddened by no cloud of sin? We cannot always have the same countenance, though the philosophers falsely boast that this was the experience of Socrates; how much less can our minds be always the same! As men have many expressions of countenance, so also do the feelings of their hearts vary. If it were possible for us to be always immersed in the waters of baptism, sins would fly over our heads and leave us untouched. The Holy Spirit would protect us. But the enemy assails us, and when conquered does not depart, but is ever lying in ambush, that he may secretly shoot the upright in heart.
2. In the Gospel according to the Hebrews, which is written in the Chaldee and Syrian language, but in Hebrew characters, and is used by the Nazarenes to this day (I mean the Gospel according to the Apostles, or, as is generally maintained, the Gospel according to Matthew, a copy of which is in the library at Cæsarea), we find, Behold, the mother of our Lord and His brethren said to Him, John Baptist baptizes for the remission of sins; let us go and be baptized by him. But He said to them, what sin have I committed that I should go and be baptized by him? Unless, haply, the very words which I have said are only ignorance. And in the same volume, If your brother sin against you in word, and make amends to you, receive him seven times in a day. Simon, His disciple, said to Him, Seven times in a day? The Lord answered and said to him, I say unto you until seventy times seven. Even the prophets, after they were anointed with the Holy Spirit, were guilty of sinful words. Ignatius, an apostolic man and a martyr, boldly writes, The Lord chose Apostles who were sinners above all men. It is of their speedy conversion that the Psalmist sings, Their infirmities were multiplied; afterwards they made haste. If you do not allow the authority of this evidence, at least admit its antiquity, and see what has been the opinion of all good churchmen. Suppose a person who has been baptized to have been carried off by death either immediately, or on the very day of his baptism, and I will generously concede that he neither thought nor said anything whereby, through error and ignorance, he fell into sin. Does it follow that he will, therefore, be without sin, because he appears not to have overcome, but to have avoided sin? Is not the true reason rather that by the mercy of God he was released from the prison of sins and departed to the Lord? We also say this, that God can do what He wills; and that man of himself and by his own will cannot, as you maintain, be without sin. If he can, it is idle for you now to add the word grace, for, with such a power, he has no need of it. If, however, he cannot avoid sin without the grace of God, it is folly for you to attribute to him an ability which he does not possess. For whatever depends upon another's will, is not in the power of him whose ability you assert, but of him whose aid is clearly indispensable.
3. C. What do you mean by this perversity, or, rather, senseless contention? Will you not grant me even so much — that when a man leaves the waters of baptism he is free from sin?
A. Either I fail to express my meaning clearly, or you are slow of apprehension.
C. How so?
A. Remember both what you maintained and also what I say. You argued that a man can be free from sin if he chooses. I reply that it is an impossibility; not that we are to think that a man is not free from sin immediately after baptism, but that that time of sinlessness is by no means to be referred to human ability, but to the grace of God. Do not, therefore, claim the power for man, and I will admit the fact. For how can a man be able who is not able of himself? Or what is that sinlessness which is conditioned by the immediate death of the body? Should the man's life be prolonged, he will certainly be liable to sins and to ignorance.
C. Your logic stops my mouth. You do not speak with Christian simplicity, but entangle me in some fine distinctions between being and ability to be.
A. Is it I who play these tricks with words? The article came from your own workshop. For you say, not that a man is free from sin, but that he is able to be; I, on the other hand, will grant what you deny, that a man is free from sin by the grace of God, and yet will maintain that he is not able of himself.
C. It is useless to give commandments if we cannot keep them.
A. No one doubts that God commanded things possible. But because men do not what they might, therefore the whole world is subject to the judgment of God, and needs His mercy. On the other hand, if you can produce a man who has fulfilled the whole law, you will certainly be able to show that there is a man who does not need the mercy of God. For everything which can happen must either take place in the past, the present, or the future. As to your assertion that a man can be without sin if he chooses, show that it has happened in the past, or at all events that it does happen at the present day; the future will reveal itself. If, however, you can point to no one who either is, or has been, altogether free from sin, it remains for us to confine our discussion to the future. Meanwhile, you are vanquished and a captive as regards two out of three periods of time, the past and the present. If anyone hereafter shall be greater than patriarchs, prophets, apostles, inasmuch as he is without sin, then you may perhaps be able to convince future generations as to their time.
It is an argument from Scripture to prove the point of the Augustinian arguer, Atticus to show the universality of sin, and thus to refute the Pelagian assertion that a man can be without sin if he wills. The Gospel of the Hebrews then exactly suits Jerome's present needs - i.e. especially the explicit citation of Jesus acknowledging he is sinless.