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.

To make glad signifies influx and reception from joy of heart.

(Reference: Apocalypse Explained 518)