And it came to pass, when he had finished speaking unto Saul, that the soul of Jonathan was knit with the soul of David, and Jonathan loved him as his own soul.
Read Chapter 18
George Leo Haydock
Soul. Pythagoras said, "that friendship is an equality, and one soul, and that the friend is another self. "It would be difficult to find two souls more tender and generous than those of David and Jonathan. (Calmet)
Josephus speaks of their friendship on another occasion, as these five verses are omitted in the Roman Septuagint (Kennicott)
Jonathan was not knit to David as a whole, but his “soul,” the higher parts, which are not cut off when the apparent and visible elements have been cut off from a person and which will not be coerced by any means, for they never move involuntarily. For the soul is free and not imprisoned in any way.… For in its primary sense, it is its nature to be wherever the mind is, and if it seems to you to be in a room, you are imagining it there in some secondary sense. So it is never prevented from being in whatever place it wishes to be; but rather, in actual fact, it can only be, and reasonably be thought to be, where the works proper to itself alone are found, and relative to that. - "Address of Thanksgiving to Origen 6.85–87"