Jesus - Arm of the LORD
KJV - Awake, awake, put on strength, O arm of the ; awake, as in the ancient days, in the generations of old. Art thou not it that hath cut Rahab, and wounded the dragon?
NLT - Wake up, wake up, O ! Clothe yourself with strength!
The arm of the Lord is Christ...He that keeps Israel neither slumbers nor sleeps; but, when we pray that He would awake, we mean that He would make it to appear that He watches over His people and is always awake to do them good.
For a more in-depth study of this verse, see MacLaren's Expositions of Holy Scripture.