When one is faced with an unavoidable danger, even if it was commanded to him by GD as in the case of Shmuel Hanavi, he is responsible to take every precaution to protect himself and not rely on his Bitachon in H'shem to protect him. This is illustrated to us by H'shem acknowledging Shmuel's fear, responding to it and not dismissing the need to take precautions.
pg 403
Nefesh Hachaim
One who does not Bench after eating is called by the Sages a
thief because the act of making a Bracha sends an abundance of Shefa down to the
world. The Bracha does not affect H'shem
since that is impossible, it increases the blessings that are sent down to the
world by the way it uplifts the higher worlds, and so one who withholds the
blessing from the world is in affect stealing the potential from everyone.
pg 403
Nefesh Hachaim
Gate 2 Chapter 4 pg 81/82
