Sermon 38 of Nahj al-Balagha: About naming of doubt as such and disparagement of those in doubt

Doubt is named doubt (al-shubhah) because it resembles truth. As for lovers of Allah, their conviction serves them as light and the direction of the right path (itself) serves as their guide; while the enemies of Allah, in time of doubt call to misguidance in the darkness of doubt and their guide is blindness (of intelligence). One who fears death cannot escape it nor can one who loves eternal life secure it.

Alternative Sources for Sermon 38
(1) Al-'Amidi, Ghurar, 98;
(2) Ibn Talhah, Matalib, I, 170;
(3) al-Jahiz, Rasa'il, 125.