This chorale prelude by J.S. Bach is a setting of the hymn "Als der gütige Gott vollenden wollt sein Wort." It features intricate contrapuntal writing with the melody woven into the texture.
Developing clarity and independence between the contrapuntal lines requires careful attention to articulation.
Als der gütige Gott vollenden wollt sein Wort is rated Henle level 4 of 9 — intermediate repertoire, roughly ABRSM grades 5–6. In the RCM system it corresponds to about level 5.
You should be comfortable at Henle level 4 — meaning you can already play level 3–4 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of Als der gütige Gott vollenden wollt sein Wort lasts about 3 minutes.
Als der gütige Gott vollenden wollt sein Wort is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.