Catechism of the Catholic Church
a, b, c, and d. Para. 526: To become a child in relation to God is the condition for entering the kingdom (Cf. Mt 18:3-4). For this, we must humble ourselves and become little. Even more: to become "children of God" we must be "born from above" or "born of God" (Jn 3:7; 1:13; 1:12; cf. Mt 23:12).
Para. 563: No one, whether shepherd or wise man, can approach God here below except by kneeling before the manger at Bethlehem and adoring him hidden in the weakness of a new-born child.