1 Corinthians 15:28
And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all. And when all things shall be subdued unto him, then shall the Son also himself be subject unto him that put all things under him, that God may be all in all.
The verse describes the inheritance of the saints as the final state in heaven when God is all and in all, everything to everyone. In that final state holiness reigns, perfect harmony with God is unmarred, and God's will is perfectly fulfilled. The heavenly sanctuary is the place of God's presence where God is all and in all, which believers are to keep ever before their minds by becoming familiar with the pattern once built on earth.
Christ is all in all in heaven, and therefore he must be our all in all on earth if we are to be ready for companionship with him there. Recognizing God as all and in all is essential, since human philosophies lead to confusion when God is not so recognized. God as all in all is to be trusted and given the place of supreme honor, rather than people being praised and exalted. In a believer's present life, God being all and in all means self is forgotten and God is magnified through thorough consecration and the use of God-given powers to spread the truth. God must be all and in all to His people as the counterworking needed in a time when Satan works through church and state, requiring increased powers and faculties through exercising God-given ability and learning to cooperate with God.
In present personal experience the verse means constantly submitting human will to God's will and human way to God's way, giving God the supremacy over peculiar ideas, plans, and self, not resting in self or dwelling on the dark side, but resting the soul in God. That experience also means striving constantly against the failings of humanity to be perfect in good work, being changed and transformed by beholding the Lord and by the renewing work of the Spirit. The grace of humility through Christ Jesus fits imperfect people for that inheritance by making them discern their own imperfections. That humility is the antidote to the apostasy of Satan with its unholy ambition and delusion. The prospect of that heavenly life calls Christians to seek God's knowledge, delight in Christ's character, and cultivate holiness now, and lack of interest in these things shows that hope of heaven is vain.