Martin Luther wrote –

“This is the heart of all Christian conviction, that the believer is assured, first of the Man ,Christ is true God in Him;  secondly, that He, Jesus, in whom God is essentially,  also is within us and we in Him. The Son comes from the Father and inheres in us; we inhere in Jesus and through Him come to the Father. Thus an endless chain has been made between Him and us and the Father, and through this union and communion, sin and death have been abolished, life and salvation have become our own.  Through faith we become one body with Christ and He with us. Through the Word of God and the Sacraments He unites Himself with us. Thus we have the three great unions: the Father and the Son united in the Deity; the man united in Christ; Christ united, becoming one with the Church.”