Exodus 14

As the children of Israel were backed into a corner where there seemed to be no escape -

"...Moses said unto the people, Fear ye not, stand still, and see the salvation of the LORD, which he will shew to you to day: for the Egyptians whom ye have seen to day, ye shall see them again no more for ever.
14 The LORD shall fight for you, and ye shall hold your peace." (Old Testament | Exodus 14:13 - 14)

In modern day, the Lord has again said -

"...dearly beloved brethren, let us cheerfully do all things that lie in our power; and then may we stand still, with the utmost assurance, to see the salvation of God, and for his arm to be revealed." (Doctrine and Covenants | Section 123:17)

The Lord tends to try our faith. It is when we have done all that lies within our power, when there seems to be no escape and answer, it is then the Lord promises us -

"...Fear ye not, stand still, and see the salvation of the LORD..." (Old Testament | Exodus 14:13)

"...behold, I do not require at their hands to fight the battles of Zion; for, as I said in a former commandment, even so will I fulfil—I will fight your battles." (Doctrine and Covenants | Section 105:14)