"As a belt clings to a person's waist, so I created Judah and Israel (God's old covenant people) to cling to me," says the LORD. "They were to be my people, my pride, my glory--an honor to my name. But they would not listen to me." -- God, through the Prophet Jeremiah, chapter 13, verse 11.
There is a sense in which I may say that the one thing, the only thing, that God has ever asked of us, is to trust Him. All of the rest (obedience, praise, sacrifice, giving, spiritual growth and maturity, etc) flow from this one thing. Unlike Judah and Israel mentioned above, the redeemed do listen to their Redeemer; and we do believe what He says. That's not complicated, just terribly difficult at times.
Now I assume that someone will want to argue that to love God is the one thing. After all, that's the great commandment of Jesus (Mt 22). But it isn't love that the Bible holds out to us as the one thing that ties us to God savingly and eternally; it's faith. And faith is simply the noun form of the word believe.
What is a Christian's trust of God like? It's like a belt clinging to a person's waist, a belt tied around us, buckled and secure. This is the picture God gives Jeremiah to share with the people. So many people, even professing Christians, can get so bent out of shape over what God asks of us. Our sinful pride bristles against God's commands. We think we know better. How foolishly faithless we can be. But have you considered this command -- Trust Me. How about Come to Me, all of you who are weak and burdened, and I will give you rest (Mt 11). That's a command. In the Bible, belief in the gospel/trust in Christ, is not offered, it's commanded. It's the one thing we ought to do. Cling to Me, says the LORD. I created you. I know you. I knitted you together in your mother's womb (Ps 139). I love you. I mean to do you good and not evil. I could go on and on and on.
We glorify God when we trust Him. That's the point of Jeremiah 13:11, along with the rest of Scripture; that only by faith are we united to Jesus for salvation, and for a life of glorifying His name.