The Hymn begins by testifying of the restoration of the Gospel. Isaiah spoke of the day when the Light and Glory of God would come forth and fill the earth in the Last Days (ISA 60:1-3). We testify that God's Light began to burst forth and fill the earth on a spring morning in 1820 when God the Father and His Son appeared to Joseph Smith.
The First Vision led to the establishment of the Church of Jesus Christ in the Latter-day and the beginning of the gathering of Israel after her long disbursement. The purpose of the Lord in gathering Israel is to gather her into His house, put Israel under the everlasting covenant, and endow her with power. This Hymn narrates the above summarized timeline. The first two verses testify of the restoration of the gospel, the third verse narrates the gathering of Israel, and the fourth verse refers to the Temple when Israel is brought before the Lord at the veil, after making covenants, in order to be endowed with power.