This is Ellen White's commentary on Revelation 14:1-5

Revelation 14:1-5 (KJV) And I looked, and, lo, a Lamb stood on the mount Sion, and with him an hundred forty and four thousand, having his Father's name written in their foreheads.
And I heard a voice from heaven, as the voice of many waters, and as the voice of a great thunder: and I heard the voice of harpers harping with their harps:
And they sung as it were a new song before the throne, and before the four beasts, and the elders: and no man could learn that song but the hundred and forty and four thousand, which were redeemed from the earth.
These are they which were not defiled with women; for they are virgins. These are they which follow the Lamb whithersoever he goeth. These were redeemed from among men, being the firstfruits unto God and to the Lamb.
And in their mouth was found no guile: for they are without fault before the throne of God.

This quote is by Ellen White
Acts of the apostle
Page 591
Loyalty now before heaven

The vision of the prophets picture[the hundred and forty-four thousand] as standing on Mount Zion, grits for holy service, clothed in white linen, which is the righteous of the saints. But all who follow the Lamb in heaven must have first follow Him on earth, not fretfully or capriciously, but in trustful, loving, willing obedience, as the flock follow the shepherd.

This is another quote by Ellen White
Thought from the Mount of Blessing
Page 69
Preparing to be with heavenly angles

Those who have learned of Christ will "have no fellowship with the unfruitful works of darkness" (Ephesians 5:11). In speech as in life, they will be simple straightfoward, and true, for they are preparing for the follow ship of those holy ones in who's mouth "was found no guilt.