My blog post on Come Follow Me: D&C 37-40
For Joseph and many of the saints, the restoration initially meant just building up a small little set of congregations. Never did any of them consider the vast work that was ahead. In D&C 37, the saints, most living in New York prior to the missionary work to the Lamanites by Oliver Cowdery, were called to the Gathering.
The concept of Gathering partially came from Joseph reworking the book of Genesis, as part of the Joseph Smith Translation of the Bible. While we call it a “translation,” it really isn’t. Joseph didn’t use ancient Hebrew and Greek documents in his rework of the Bible. Instead, he used an English Bible purchased at the Grandin book store. Joseph was less concerned with the language and grammar, and more focused on finding the “plain and precious” things that had been lost out of the Bible. Rather than a translation, it would be a series of refining revelations.