Referent: Mormon is referencing a text from the brass plates:
Joshua 10:12-14
12 ¶ Then spake Joshua to the LORD in the day when the LORD delivered up the Amorites before the children of Israel, and he said in the sight of Israel, Sun, stand thou still upon Gibeon; and thou, Moon, in the valley of Ajalon.
13 And the sun stood still, and the moon stayed, until the people had avenged themselves upon their enemies. Is not this written in the book of Jasher? So the sun stood still in the midst of heaven, and hasted not to go down about a whole day.
14 And there was no day like that before it or after it, that the LORD hearkened unto the voice of a man: for the LORD fought for Israel.
Mormon alludes to the text in Joshua as another model for the control of the Lord over the elements of nature. Even the earth obeys in its orbit.