What joy and fellowship there is in gatherings where the newly-saved are present! In the spiritual realm, as well as in the physical, everyone loves a baby! But the joy that fills the hearts of loving parents is turned to bitter sorrow and disappointment if their babe fails to grow. The latter condition is as unspeakably sad and embarrassing as the former is joyous. Just so it is in the realm of the spirit. The “carnal” Christian has failed to grow. He continues in a state of protracted infancy. He must be kept exclusively on a milk diet because, though saved for years, he is still unable to “bear,” or digest, solid food, still “unskillful in the Word” and needing to be taught the elementary things.
Retarded spiritual growth is evidenced in many ways, all of which come under the heading of carnality or fleshliness. The Corinthians, so sternly rebuked for their carnality by the Apostle Paul, are said to have been careless about morals (I Cor. 5:1), puffed up (I Cor. 4:18; 5:2), inconsiderate of each other (I Cor. 6:1-7; 8:1,9,12), stingy (II Cor. 8:6-11; 11:7-9). While possessing the Spirit, they walked after the flesh.
Thus Peter’s exhortation to “newborn babes” to “desire the pure milk of the Word” that they may “grow thereby,” is prefaced by the words: “Wherefore laying aside all malice, and all guile, and hypocrisies, and envies, and all evil speakings” (I Pet 2:1). The carnal nature is not appropriate soil for spiritual growth. source