The word(s) "frail" appears 2 time(s) in 2 verse(s) in Quran in Mohsin Khan translation.

(1) The likeness of those who take (false deities as) Auliya' (protectors, helpers) other than Allah is the likeness of a spider who builds (for itself) a house; but verily, the frailest (weakest) of houses is the spider's house - if they but knew.

(2) And the heaven will be rent asunder, for that Day it (the heaven) will be frail and torn up.