Like newborn babies, you should crave (thirst for, earnestly desire) the pure (unadulterated) spiritual milk, that by it you may be nurtured and grow unto [completed] salvation (1 Peter 2:2)
Scripture tells us to crave because this appetite doesn't always come to us naturally.
How do we develop this appetite?
We must start drinking. Newborn infants very often are very fussy and sometimes reject the very milk they are crying for. It's only after they get a taste of it will they hungrily gulp it.
But you are a chosen generation, a royal priesthood, a holy nation, His own special people, that you may proclaim the praises of Him who called you out of darkness into His marvelous light; who once were not a people but are now the people of God, who had not obtained mercy but now have obtained mercy. (1 Peter 2:9-10)
Peter uses wording from Exodus 19:5–6, where God told the children of Israel, “if you will indeed obey My voice and keep My covenant, then you shall be a special treasure to Me above all people; for all the earth is Mine. And you shall be to Me a kingdom of priests and a holy nation.”
Chosen generation
When God describes you as “a chosen generation,” it means you belong to a new class of species with divine genetic makeup. No wonder the Bible in Romans 8:37 says we are more than conquerors, meaning your lineage is one of champions and victors.
We are a royal priesthood
Under the Old Covenant, the priesthood and royalty were separated. In Christ, we are now “kings and priests” (Revelation 1:6), prepared for walking with Him in the light or warring beside Him against the hosts of darkness.
We are made a holy nation
Since we are born of Jesus’ blood, from every nation under heaven
Finally, He calls us His own special people
God’s intention has always been to call forth a people who will proclaim His praise and spread His blessing throughout the earth.
“who once were not a people but are now the people of God, who had not obtained mercy but now have obtained mercy.”
Apostle Peter is making it clear that Gentile believers are also God’s chosen race during this age.
Having been delivered from the spiritual darkness of ignorance, error, sin, and misery; and now, though His mercy given to us, we walk in His marvelous light.