People were bringing even infants to him that he might touch them,* and when the disciples saw this, they rebuked them. Jesus, however, called the children to himself and said, “Let the children come to me and do not prevent them; for the kingdom of God belongs to such as these. Amen, I say to you, whoever does not accept the kingdom of God like a child will not enter it”.

Luke 18:15-17

The adverb “even” or “also” suggests that mothers were bringing little children to meet our Lord at the same time as others brought sick people to him.

“That he might touch them”: the sight of the curing of the sick naturally led the people to bring their children to Jesus, to be assured of good health by being touched by him; in the same way as the lady with the issue of blood thought she could be cured by touching him (cf. Mt 9:20-22). The parallel text in St. Matthew is a little more specific: “Children were brought to him that he might lay his hands on them and pray”, that is, to have him bless them.

The episode of Jesus and the children corroborates the teaching about humility contained in the parable of the Pharisee and the tax collector.

“Why, then, does he say that children are fit for the Kingdom of heaven? Perhaps because usually they are without malice, nor are they deceptive, nor do they dare to avenge themselves; they have no experience of lust, do not covet riches and are not ambitious. But the virtue of all this does not lie in ignorance of evil, but in its rejection; it does not consist in not being able to sin but rather in not consenting to sin. Therefore, the Lord is not referring to childhood as such, but to the innocence which children have in their simplicity.”

St. Ambrose
Expositio Evangelii sec. Lucam, in loc.

Receiving the Kingdom of God like children, becoming children before God, means

“renouncing our pride and self-sufficiency, recognizing that we can do nothing by ourselves. We must realize that we need grace, the help of God our Father, to find our way and keep to it. To be little, you have to abandon yourself as children do, believe as children believe, beg as children beg.”

J. Escrivá
Christ is passing by, 143

Catechism

913

"Thus, every person, through these gifts given to him, is at once the witness and the living instrument of the mission of the Church itself 'according to the measure of Christ's bestowal'."