Theophylact of Ohrid — on 1Tim 6:15-16 (Commentary on 1 Timothy)

“That is, at a fitting, predetermined time. Therefore do not grieve that it has not yet come. And the apostle says this for consolation, so that Timothy would not look upon the seemingly blissful goods of this world, but would fix his gaze upon the One alone Who is blessedness itself, in Whom there is neither sorrow nor sighing; so that he would not fear any earthly rulers and kings. At the same time, he prepares him for what His coming will reveal. For He is "the only Mighty One." All of this is said about the Son. And the word "only" the apostle used to contrast Him with men, or with false gods, but not in relation to the other Persons of the Most Holy Trinity. The Lord alone possesses immortality by essence; angels, although immortal, are so not by nature but by grace. Therefore, they do not have immortality, but are partakers of immortality.”