(The following is taken from DAVID GUZIK COMMENTARY ON THE BIBLE, Studylight.org)
Likewise you younger people, submit yourselves to your elders. Yes, all of you be submissive to one another, and be clothed with humility, for “God resists the proud, but gives grace to the humble.” Therefore humble yourselves under the mighty hand of God, that He may exalt you in due time, casting all your care upon Him, for He cares for you.
Likewise you younger people: Peter begins this word of humility to you younger people, in contrast to the elders he has just addressed. But he soon realizes that it is of application to all of you. This word to be submissive to one another and be clothed with humility applies to everyone, but perhaps especially to the young.
Clothed with humility: Humility is demonstrated by submission. It is the ability to cheerfully put away our own agenda for God’s, even if God’s agenda is expressed through another person.
Be clothed with humility: “Be clothed” translates a rare word that refers to a slave putting on an apron before serving, even as Jesus did before washing the disciple’s feet (John 13:4).
For “God resists the proud, but gives grace to the humble.” Humility is essential to our relationship with God. If we want to walk in God’s grace (His unmerited favor) then we must lay aside our pride and be humble - not only to Him but also to one another.
Grace and pride are eternal enemies. Pride demands that God bless me in light of what I think I deserve. Grace will only deal with me on the basis what is in God (love), not on the basis of anything in me.
“Pride is one of the most detestable of sins; yet does it find lodgment in earnest souls, though we often speak of it by some lighter name. We call it - independence, self-reliance. We do not always discern it in the hurt feeling, which retires into itself, and nurses its sorrows in a sulk . . . We are proud of our humility, vain of our meekness; and, putting on the saintliest look, we wonder whether all around are not admiring us for our lowliness.” (Meyer)
That He may exalt you in due time: If God has us in a humble place at the present time, we must submit to God’s plan. He knows the due time to exalt us, though we often think we know that time better than God does.
Casting all your care upon Him, for He cares for you: True humility is shown by our ability to cast our care upon God. It is proud presumption to take things into our own worry and care about things that God has promised to take care of (Matthew 5:31-34).
Sometimes we need to call worry and inappropriate care exactly what it is: pride and unbelief, and a desire to usurp God’s place as our providing, caring Father.
We often judge the parents by the children. When a child of God is full of worry and fear, doesn’t the world have reason to believe that their Father in heaven doesn’t care for them? Our worry and fear reflects poorly - in an unfair way - upon God.