Here are 2 more spirituals that contains the "miry clay" line: Rev. Gary Davis' O GLORY! HOW HAPPY I AM and Kathleen Battle & Jessye Norman's YOU CAN TELL THE WORLD.

The origin of the "miry clay" metaphor is probably Psalm 40 [KJV]:

1. I waited patiently for the LORD; and he inclined unto me, and heard my cry.
2. He brought me up also out of an horrible pit, out of the miry clay, and set my feet upon a rock, and established my goings.