Aaron was the brother of Moses. He symbolizes two things, at different stages of the story.

During the first part of the exodus, when he was Moses' spokesperson, Moses represents the Word as it truly is, as it is understood in heaven, while Aaron represents the Word in its external sense, as it is understood by people in the world. This is why Aaron talks for Moses, and the Lord says of him "he shall be as a mouth for you, and you shall be to him as God." (Exodus 4:16)

Later, after the Tabernacle was built and he was inaugurated as high priest (see Leviticus 8,9), Aaron represents the Lord as to the Divine Good, and Moses represents the Lord as to the Divine Truth.

In Exodus 28:1, Aaron signifies the conjunction of Divine Good with Divine Truth in the Divine Human of the Lord. (Arcana Coelestia 9806, 9936)

In Exodus 32:1, Aaron represents the external of the Word, of the church, and of worship, separate from the internal. (Arcana Coelestia 10397)

In Exodus 4:14, before he was initiated into the priesthood, Aaron represents the doctrine of good and truth. (Arcana Coelestia 6998)

5951. 'And the sons of Israel did so' means a putting into effect by the spiritual truths within the natural. This is clear from the meaning of 'they did' as a putting into effect; and from the representation of 'the sons of Israel' as the spiritual truths within the natural, dealt with in 5414, 5879. What spiritual truths within the natural are must be stated: The truths of faith if separate from man, spirit, or angel are not in fact the truths of faith, for they are not attached to a recipient in whom they become such truths. But when they are attached to man, spirit, or angel as their recipient they then become the truths of faith, yet varyingly so according to each individual's state of life. With those who are just beginning to learn them they are no more than factual knowledge. If after that those people truly revere them they go on from being factual knowledge to become the truths of the Church. When however they have an affection for those truths and lead lives in keeping with them, they become spiritual truths; for the good of love and charity, which has its origin solely in the spiritual world, then enters in and brings life to them. For having an affection for them and leading a life in keeping with them stem from that good.

[2] What truths, called the truths of faith, are like with those who lead lives in keeping with them, and with those who do not, has been shown to me. With people who do not lead lives in keeping with them those truths have manifested themselves as white threads; and with people who knew those truths yet did nothing good at all they were fragile ones. But with people who do lead lives in keeping with them those truths have manifested themselves as fibres extending from the brain, which were filled with spirituous fluid and were soft. Thus these latter truths had life in them, the former did not. From all this one may recognize that the nature of the truths present with people depends on the individual's state of life. The truths which 'the sons of Jacob' represent are not as yet spiritual truths because they have not as yet been made matters of life. But the truths represented by those men as 'the sons of Israel' are spiritual ones because, having been made matters of life, the good of love and charity has entered them. Such truths are meant here because now the subject is the initial stage in the joining of the truths within the natural, which are 'the sons of Jacob', to internal good, which is 'Joseph', through the intermediary, which is 'Benjamin', and also through spiritual good, which is 'Israel'.