How many letters does the top answer for “of or pertaining to sacred writing.” have?

The most common answer is hierographic (12 letters).

Crossword clue: of or pertaining to sacred writing.

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

hierographic 12 letters web-def

Of or pertaining to sacred writing.

hierographical 14 letters web-def

Of or pertaining to sacred writing.