Thou shalt see now whether My word shall come to pass unto thee or not.
Numbers 11:23
"GOD had made
a positive promise to Moses that for the space of a 
whole month He
would feed the vast host in the wilderness with flesh. Moses, being
overtaken by a fit of unbelief, looks to the outward means, and is at a
loss to know how the promise can be fulfilled.
He looked to the creature
instead of the Creator.
Q: But doth the Creator expect the creature to
fulfil His promise for Him?
A: No; He who makes the promise ever fulfils it
by His own unaided omnipotence. If He speaks, it is done—done by
Himself.
---His promises do not depend for their fulfillment upon the
co-operation of the puny strength of man.
We can at once perceive the
mistake which Moses made. And yet how commonly we do the same! God has
promised to supply our needs, and we look to the creature to do what God
has promised to do; and then, because we perceive the creature to be
weak and feeble, we indulge in unbelief. Why look we to that quarter at
all?
Q: Will you look to the north pole to gather fruits ripened in the
sun?"
Charles Spurgeon