From Clavierübung Part I. For each of the 13 hymns treated in his Clavierübung, Krebs wrote a Praeambulum (only loosely connected to the melody, e.g. built on a characteristic interval or motiv), a chorale (often a bicinium), and the hymn itself with figured bass.
Published by Edition Breitkopf, but also available on imslp.
"Von Gott will ich nicht lassen" is no Advent hymn, but we use the same melody for the Advent hymn "Mit Ernst, o Menschenkinder".