What is the Pasuk referring to when it writes "Acheil Teis Pachd'cha ... Tachas Kol ha'Shamayim"?
Rashi: This teaches us
that during the battle against Og, the sun (and moon - Targum Yonasan) stood still
(for thirty-six hours, to allow the army to finish the job
See also Ba'al ha'Turim.
Ramban: As the Pasuk explains later in 3:21. Otherwise, what would be the connection between the battle with two kings and the fear of Moshe on all the nations? Hence the Torah writes "Begin to inherit his land" (Pasuk 31)