The interpretation timeline
Mark 4:9 Douay-Rheims

And he said: He that hath ears to hear, let him hear.

A.D. 407 – 1832 3 witnesses

Patristic

before A.D. 750
407
A.D.
John Chrysostom Patristic
A.D. 347–407
“(ubi sup.) This, however, the greater portion of the seed is not lost through the fault of the owner, but of the earth, which received it, that is, of the soul, which hears. And indeed the real husbandman, if he sowed in this way, would be rightly blamed; for he is not ignorant that rock, or the road, or thorny ground, cannot become fertile. But in spiritual things it is not so; for there it is possible that stony ground may become fertile; and that the road should not be trodden down, and that the thorns may be destroyed, for if this could not take place, he would not have sown there. By this therefore He gives to us hope of repentance. It goes on, And he said unto them, He that hath ears to hear, let him hear.”
Source

Post-Reformation

c. 1650 – 1900
1771
A.D.
John Gill Reformed
1697–1771
“And when he was alone,.... After the multitude was dismissed, and he either remained in the ship, or left it, and retired to some private place, it may be to Simon's house in Capernaum. The Syriac, Persic, and Ethiopic versions read, "when they were alone"; meaning as follows, they that were about him with the twelve; that is, such disciples of his, who, besides the twelve, constantly attended him; perhaps those who now were, or hereafter were the seventy disciples. The Vulgate Latin reads, "the twelve that were with him". In Beza's most ancient copy it is read, "his disciples"; and to this agrees the Persic version; and so the other evangelists, Matthew and Luke, relate, that his disciples came and asked of him the parable; the meaning of it, and why he chose this way of speaking to the people, Mat 13:10, though that word may include others besides the twelve.”
Source
1832
A.D.
Adam Clarke Methodist
1762–1832
“And he said - He that hath ears to hear, let him hear - The Codex Bezae, later Syriac in the margin, and seven copies of the Itala, add, και ὁ συνιων συνιετω, and whoso understandeth, let him understand.”
Modern · 1953 →

The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.