At that time, says the Lord, will I be the God of all the families of Israel, and they shall be my people. — Jeremiah 31:1
For you are a temple of the living God. Even as God said, "I will dwell in them, and walk in them; and I will be their God, and they will be my people." — 2 Corinthians 6:16

Author
Charles Spurgeon
Summary: God and his people belong to one another: he is our portion, and we are his special treasure. This truth offers profound comfort and moves us to mutual consideration. Since God thinks of us and works on our behalf, our thoughts should sincerely turn toward him and ask how we may serve him. This bond also produces fellowship: God dwells and walks with us, and we abide and walk with him. Therefore, we long to treat him truly as our God, trusting in him and serving him with love, worship, reverence, and obedience. We need his grace to know him in this way, through Jesus Christ our Lord.
Here there is a mutual interest. Each belongs to the other. God is the portion of His people, and the chosen people are the portion of their God. The saints find that God is their chief possession, and He regards them as His peculiar treasure. What a mine of comfort for the believer lies hidden in this fact!
This happy condition of mutual interest leads to mutual consideration. God will always think of His own people, and they will always think of Him. On this day, my God will perform all things for me; what can I do for Him? My thoughts should run toward Him, for He thinks of me. I must make sure that it is so, and I must not be content merely to admit that it ought to be so.
This, moreover, leads to mutual communion. God dwells in us, and we dwell in Him; He walks with us, and we walk with God. What happy communion this is! Oh, that I may receive grace to treat the Lord as my God: to trust in Him, and to serve Him as His Deity deserves! Oh, that I might love, and worship, and reverence, and obey Jehovah in spirit and in truth! This is the desire of my heart. When I attain it, I shall have found my heaven. Lord, help me! Be my God, helping me to know You as my God, through Jesus Christ our Lord.
Source: The Cheque Book of the Bank of Faith. Translated by Allan Roman.
http://www.spurgeon.com.mx/chequera/meditames/abril.pdf