Arcana Coelestia #6730
6730. 'To wash at the river' means worship involving the use of falsity. This is clear from the meaning of 'washing' as purification from what is understood spiritually by filth, dealt with in 3147, worship consequently being meant since worship takes place for the sake of purification; and from the meaning of 'the river', in this case the river of Egypt, as falsity, dealt with in 6693.
Child
A child is a young boy or girl in the care of parents, older than a suckling or an infant, but not yet an adolescent. "Children" are sometimes used as a name for a large group of descendants of one person, such as the Children of Israel, or even all human beings as the Children of Men. A child represents innocence and charity, where innocence is the willingness to be led, and charity is love. This is why Jesus blessed them and suggested that we all become like children in order to enter heaven.