Widor's '3 Motets' Op. 23 are sacred compositions that exhibit his characteristic contrapuntal skill and rich harmonic language.
Students should concentrate on developing sophisticated contrapuntal independence between voices.
3 Motets (Op.23) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
3 Motets (Op.23) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.