Joy

3 Nephi 28:9-10

"...for ye have desired that ye might bring the souls of men unto me, while the world shall stand.

And for this cause ye shall have fulness of joy; and ye shall sit down in the kingdom of my Father; yea, your joy shall be full, even as the Father hath given me fulness of joy; and ye shall be even as I am, and I am even as the Father; and the Father and I are one;"

Here, a fulness of joy is said to be bringing souls unto Christ.  Missionary work brings a fulness of joy. The gospel is joy, so sharing it and spreading it with all of God's children is delightful!