(Devarim, Ibid.) "with a strong hand": This is the pestilence, as it is written (Shemoth 9:3) "Behold, the hand of the L-rd is in your cattle in the field … a very sore pestilence."
"and with an outstretched arm": This is the sword, as it is written (Joshua 5:13) "with his sword sh'lufah in his hand": ("sh'lufah" =) outstretched.
"and with great fear": This is revelation of the Shechinah, as it is written (Devarim 4:34) "Or has a god ever done miracles to come and take for himself a nation with trials, with signs, and with wonders, and with war, and with a strong hand, and with an outstretched arm, and with great fears, before your eyes?"