Blest are the undefiled in heart,
Whose ways are right and clean;
Who never from Thy law depart,
But fly from every sin.
Blest are the men that keep Thy Word,
And practice Thy commands;
With their whole heart they seek the Lord,
And serve thee with their hands.
Great is their peace who love Thy law;
How firm their souls abide!
Nor can a bold temptation draw
Their steady feet aside.
Then shall my heart have inward joy,
And keep my face from shame,
When all Thy statutes I obey,
And honor all Thy Name.
Trinity Hymnal #557
Words by Isaac Watts, 1719 (modified to remove those mean verses about God hating vile sinners and such)
From Psalm 119
Sola Fidelity 