The word Peter uses means “crave” and describes exactly the significance of the lusty cry of an infant, which no distraction will satisfy. This particular verb is the central command of the present paragraph. Whereas an infant will naturally crave a feed, Peter’s readers need to be commanded to crave that feed. That is because there are hindrances remaining in regenerated hearts that obstruct the longing for milk. Those hindrances include vices such as malice, deceit, hypocrisy, envy, and slander, and form the reason why Peter would have his readers to put them away (1 Peter 2:1). By doing so the reborn develop an increased craving for drink.
2 Like newborn infants, long for the pure spiritual milk, that by it you may grow up into salvation