# the redemption money

This refers to the money that Moses collected. Some translations use "ransom".

# to his sons

Here "his" refers to Aaron

# he was told to do by Yahweh's word, as Yahweh had commanded him

These two phrases mean basically the same thing and are combined for emphasis. 

# he was told to do by Yahweh's word

"that Yahweh had told him to do"