[Avodah] Moshe Rabbenu's Punishment Amalek

[Michael Kopinsky]

On 2/13/07, Meir Rabi <meirabi at optusnet.com.au> wrote:
> Moshe Rabbenu was punished, became weak and had to sit down and have his
> arms supported because he had delegated the battle to Yehoshua. What should
> he have done? The event provided BNY with a remarkable illustration of the
> power of Tefillah. Was that to be substituted for MR leading the Jews in
> war?
What is your source for this understanding? (that the punishment was
because he delegated)