Aaron,

"And give me a Minister
From my family,
"Aaron, my brother;
"Add to my strength
Through him.
"And make him share
My task:
"That we may celebrate
Thy praise without stint,
"And remember Thee
Without stint:
"For Thou art ever seeing
(God) said: "Granted
Is thy prayer, O Moses!"

Literally, "Strengthen my back with him". A man
strength lies in his back and backbone so that he can
stand erect and boldly face his tasks.

The requests that Moses makes are inspired, not by
earthly but by spiritual motives. The motive, expressed in
the most general terms, is to glorify God, not in an occasional
way, but systematically and continuously, "without stint".

The celebration of God's praise and remembrance is one form of
showing gratitude on the part of Moses for the Grace which God
has bestowed upon him.