(Ibid. 2) "Six days may work be done": And another verse states (Ibid. 20:9): "Six days shall you work." (How are these to be reconciled?) When Israel do the will of the L-rd, their work is done by others. (Hence, the first verse.)
When Israel Does the Will of God, Their Work Is Done by Others
Mekhilta Tractate Shabbata 2:4