Deuteronomy 14:23

Ver. 23. That thou mayest learn to fear the Lord thy God always— That is, that thou mayest be accustomed to the worship of the only true God; for that is sometimes the meaning of the word to learn. Thus the design of this and their other annual feasts was, to preserve them steadfast in their religion; for, by this solemn rite of eating and drinking together, in the presence of Jehovah, at the place of his public worship, they professed their adherence to the service of the true God, in opposition to all false deities.