(Wikipedia) Luther was a German professor of theology, composer, priest, and monk, and a seminal figure in the Protestant Reformation. Luther taught that salvation and, consequently, eternal life are not earned by good deeds but are received only as the free gift of God's grace through the believer's faith in Jesus Christ as redeemer from sin.

The first line of that song was “A Mighty Fortress is Our God”

"A Mighty Fortress" is one of the best loved hymns of the Lutheran tradition and among Protestants more generally. It has been called the "Battle Hymn of the Reformation" for the effect it had in increasing the support for the Reformers' cause.

Compiled and published by Rev. William Booth, General, in 1904 - its title was THE SALVATION SOLDIER’S – SONG BOOK!

Above this song at the top of the page you will find the following:

GOD THE FATHER
Person and Praise

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A mighty fortress is our God, a bulwark never failing;
Our helper He, amid the flood of mortal ills prevailing:
For still our ancient foe doth seek to work us woe;
His craft and pow’r are great, and, armed with cruel hate,
On earth is not his equal.

Did we in our own strength confide, our striving would be losing,
Were not the right Man on our side, the Man of God’s own choosing:
Dost ask who that may be? Christ Jesus, it is He;
Lord Sabaoth, His Name, from age to age the same,
And He must win the battle.

And though this world, with devils filled, should threaten to undo us,
We will not fear, for God hath willed His truth to triumph through us;
The Prince of Darkness grim, we tremble not for him;
His rage we can endure, for lo, his doom is sure,
One little word shall fell him.

That word above all earthly pow’rs, no thanks to them, abideth;
The Spirit and the gifts are ours through Him Who with us sideth;
Let goods and kindred go, this mortal life also;
The body they may kill: God’s truth abideth still,
His kingdom is forever.

The above song is Number One in our current Song Book as well. It appears under the heading:

THE ETERNAL GOD
God the Father, Holy, Loving, Creator, and Ruler