Alma 21:1 - 21:5
Alma 21:1 Now when Ammon and his brethren separated themselves in the borders of the land of the Lamanites, behold Aaron took his journey towards the land which was called by the Lamanites, Jerusalem, calling it after the land of their fathers’ nativity; and it was away joining the borders of Mormon.
When the boys split up at the Lamanite border, Aaron travel to the area called Jerusalem by the Lamanites which was near the land of Mormon. The area was named after the land of Jerusalem that their ancestors originally came from.
It rather reminds me of towns in New England. Nearly all of the original towns the puritans settled were named after English towns they had come. However, when the saints came to the Great Salt Lake valley, they used Book of Mormon names for places rather than the towns they came from.
Alma 21:2 Now the Lamanites and the Amalekites and the people of Amulon had built a great city, which was called Jerusalem.
The actually city of Jerusalem in the land of Nephi was built by the Lamanites, Amalekites and Amulonites.
Alma 21:3 Now the Lamanites of themselves were sufficiently hardened, but the Amalekites and the Amulonites were still harder; therefore they did cause the Lamanites that they should harden their hearts, that they should wax strong in wickedness and their abominations.
Now the Lamanites were certainly hard cases but the mixing with the Amalekites and made them even worse in their attitude towards the Nephites.
Alma 21:4 And it came to pass that Aaron came to the city of Jerusalem, and first began to preach to the Amalekites. And he began to preach to them in their synagogues, for they had built synagogues after the order of the Nehors; for many of the Amalekites and the Amulonites were after the order of the Nehors.
When Aaron entered the city of Jerusalem, he went to the synagogues of the Amalekites to preach. The Amalekites had organized themselves after the manner of the Nehors because they were of that order.
Alma 21:5 Therefore, as Aaron entered into one of their synagogues to preach unto the people, and as he was speaking unto them, behold there arose an Amalekite and began to contend with him, saying: What is that thou hast testified? Hast thou seen an angel? Why do not angels appear unto us? Behold are not this people as good as thy people?
One day as Aaron was preaching in one of their synagogues, there was a Amalekite who began to argue with Aaron saying that Aaron may have seen and angel, but why have to the Amalekites not seen angels. Are not the Amalekites just a good as the Nephites.
Good question, why have we all not seen an angel? First it is a manner of necessity. Is it necessary that we all see an angel. Not really, we all have administrating angels or guardian angels all around us who look after us. We have the Holy Ghost to suggest things to do. Second, angelic appearances are for special purposes and nearly all of us have little need for that. Most of the occurrences I know about were usually to get someone to change or prepare for an important event.