that we may preserve unto them the words which have been spoken by the mouth of all the holy prophets - 1 Nephi 3:20

1 Nephi 3:19-20

And behold, it is wisdom in God that we should obtain these records, that we may preserve unto our children the language of our fathers;
And also that we may preserve unto them the words which have been spoken by the mouth of all the holy prophets, which have been delivered unto them by the Spirit and power of God, since the world began, even down unto this present time.
1 Nephi 3:19-20

Read in scriptures: http://bit.ly/2wtlHNI