'A trough,' as in Genesis 24:20, signifies the 'good of truth,' because the water in the trough signifies truth, and the trough itself has the same meaning as 'wood,' that is, good.

The good of truth is produced from good by truth. It is an offspring born of truth as a mother and good as a father. All genuine good in the natural self is from the marriage of good and truth in the rational.

This is what is called the good of truth, and is the meaning of 'trough' in the Word, as a place to receive water. 'A little trough,' as in Exodus 2:16, signifies the doctrine of charity. This because it is a wooden trough which holds water drawn from a well for flocks to drink. Anything wooden, in the internal sense, signifies the good of charity. 'To draw' signifies being instructed. 'The water' which is drawn signifies the truth of faith. 'The well' which it is drawn from signifies the Word. 'To give the flocks to drink' signifies instruction in good from the Word. This makes it clear that 'a little trough' denotes the doctrine of charity.

(Reference: Arcana Coelestia 3095)