Decide what the purpose of the ancient text is. Obviously, you want the players to be able to read the text in some way. As someone mentioned before they either need a rosetta stone (quest to search for a mcguffin), or a person that can do the translating (quest to find person), or a spell (quest for a scroll, or "good job preparing, wizard!"), or a combination between 2 & 3 use speak with dead on a corpse that knew the ancient language.

In any case, someone knowing comprehend languages bypasses a single quest which you can make up for later. Or maybe the rest of the party has to hold of some bad guys without the wizard's help while he is reading the ancient text. Or the room starts flooding and the party has to find a way to stop the flooding (or ceiling slowly lowering).

Decide what the purpose of the ancient text is. Obviously, you want the players to be able to read the text in some way. As someone mentioned before they either need a rosetta stone (quest to search for a mcguffin), or a person that can do the translating (quest to find person), or a spell (quest for a scroll, or "good job preparing, wizard!") or as a combination of 2 & 3: use speak with dead on a corpse that knew the ancient language.

In any case, someone knowing comprehend languages bypasses a single quest which you can make up for later. Or maybe the rest of the party has to hold of some bad guys without the wizard's help while he is reading the ancient text. Or the room starts flooding and the party has to find a way to stop the flooding (or ceiling slowly lowering).