Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is. Now are we the sons of God - He speaks of those who are begotten of God, and who work righteousness. See the preceding chapter.
And it doth not yet appear what we shall be - Ουπω εφανερωθη· It is not yet manifest; though we know that we are the children of God, we do not know that state of glorious excellence to which, as such, we shall be raised.
When he shall appear - Εαν φανερωθη· When he shall be manifested; i.e., when he comes the second time, and shall be manifested in his glorified human nature to judge the world.
We shall be like him - For our vile bodies shall be made like unto his glorious body; we shall see him as he is, in all the glory and majesty both of the Divine and human nature. See Philippians 3:21; and John 17:24 : Father, I will that they also whom thou hast given me be with me where I am, that they may behold my glory. John had seen his glory on the mount when he was transfigured; and this we find was ineffably grand; but even this must have been partially obscured, in order to enable the disciples to bear the sight, for they were not then like him. But when they shall be like him, they shall see him as he is - in all the splendor of his infinite majesty.