The word(s) "firmest" appears 3 time(s) in 3 verse(s) in Quran in Muhammad Habib Shakir translation.

(1) There is no compulsion in religion; truly the right way has become clearly distinct from error; therefore, whoever disbelieves in the Shaitan and believes in Allah he indeed has laid hold on the firmest handle, which shall not break off, and Allah is Hearing, Knowing.

(2) And whoever submits himself wholly to Allah and he is the doer of good (to others), he indeed has taken hold of the firmest thing upon which one can lay hold; and Allah's is the end of affairs.

(3) Surely the rising by night is the firmest way to tread and the best corrective of speech.