Spirit of Prophecy

-ADVICE TO UNDERSTANDING ISAIAH:
1) liken scriptures to our day
2) understand manner in which Jesus prophesied
3) understand geography/culture of ancient Israel--study regions and manners of Jews
4) understand consequences of actions
5) read scriptures with "spirit of prophecy"

Wherefore, hearken, O my people, which are of the house of Israel, and give ear unto my words; for because the words of Isaiah are not plain unto you, nevertheless they are plain unto all those that are filled with the spirit of prophecy. But I give unto you a prophecy, according to the spirit which is in me; wherefore I shall prophesy according to the plainness which hath been with me from the time that I came out from Jerusalem with my father; for behold, my soul delighteth in plainness unto my people, that they may learn. -2 Nephi 25:4

And I fell at his feet to worship him. And he said unto me, See thou do it not: I am thy fellowservant, and  of thy brethren that have the testimony of Jesus: worship of God: for the testimony of Jesus is the spirit of prophecy.
-Revelation 19:10

See also:
3 Nephi 3:19
Jacob 1:6, 4:6
Alma 3:27, 4:13, 4:20, 5:47, 6:8, 8:24, 9:21, 10:12, 12:7, 13:26, 16:5, 17:3, 23:6, 25:16, 37:15, 43:2,
Helaman 4:12, 4:23
D&C 11:25, 131:5
Joseph Smith--History 1:73