Humble yourselves, therefore, under the mighty hand of God so that at the proper time he may exalt you, casting all your anxieties on him, because he cares for you. 1 Peter 5:6-7
A few things to note:
1. The phrase “humble yourselves” is passive in the greek, with the sense of “be humbled” or “allow yourself to be humbled by God”
2. The clause “casting all your anxieties” is dependent to v.6 and explains the way in which we humble ourselves
3. The phrase “all your anxieties” is literally “the whole of your anxiety,” as in the totality of it
Our refusal to cast all of our concerns on God and be totally dependant on him is rooted in pride. We seek to be self-sufficient and do things of our own resources. We are humbled by casting all of our anxieties (concerns, cares, desires, fears) on him. The previous verse says, “God opposes the proud but gives grace to the humble.” When we are proud, God will often oppose us to humble us and bring us to the point of casting all of our cares on him, trusting that he cares for us. This is part of his work of conforming us to the image of his Son.
This page has a great in depth study on this verse: