Emunah and Bitachon

Emunah is knowing Hashem runs the world and that everything which occurs is part of the Divine Plan. Bitachon is the internalization of this idea as it applies to one's personal life.

Vilna Gaon: The purpose of all mitzvot is to bring us to bitachon.

Chavakuk reduced the mitzvot to one principle - "וצדיק באמונתו יחיה" - Emunah.

Why was Sarah reprimanded for laughing when hearing she would have a son whereas Avraham was not?