John 14:20
At that day ye shall know that I am in my Father, and ye in me, and I in you.
At that day ye shall know,.... The things they should know, or the objects of knowledge are,
that I am in my Father; in his bosom, in union with him, partaker of the same nature, perfections, and glory with him, and equal to him:
and you in me: that they were in union with him as the branches in the vine, and as the members are in the head, and how they were loved in him, chosen in him, righteous in him, risen with him, and made to sit together in heavenly places in him:
and I in you; formed in their hearts, living in them, dwelling in them, as in his temples, and filling them with grace and glory. The knowledge of these things promised, designs a more clear and distinct knowledge of them; something of them was known already, but not so perfectly as should be hereafter; and this does not suppose that these unions between the Father and Christ, and between Christ and his people, shall then begin to be; for as the union between the Father and the Son is as eternal as themselves; so the union between Christ and his people, as he is the head and representative of them, is as early as his investiture with the office of a Mediator, and his suretyship engagements for them, which were from eternity; and are the ground, and foundation of his being in them, and they in him in the effectual calling; nor does it suggest that they shall begin to be known; only that they shall be known in a more perfect manner: the time when this will be, is "at that day": meaning either when he should "live" in the body again, be raised from the dead, when he should he declared to be the Son of God with power, when it would appear, that he had the same power with the Father, by raising himself from the dead, and when he would rise as a public head representing them, for their justification, and they should see themselves justified and discharged in him; or the day of "Pentecost", when "the Spirit of truth", he promises to pray for, should come to them in an extraordinary manner, and lead them into the knowledge of these things; or the last day, the resurrection morn, when, by virtue of union to Christ, the saints shall rise and "live" with him for ever, and shall have a perfect knowledge of these several unions; see John 17:21.