The udder of the cow has milk in it. The milk has ghee (clarified butter) in it. But the ghee cannot be a source of strength to one, as such. The milk has to be drawn, yeast added to curdle it, butter has to be churned out and clarified to produce the ghee which, when consumed by one can give one strength. So too, though God is omnipresent, He has to be discovered and cognised in order to realise the bliss. Like oil in mustard, butter in yoghurt, like water inside the earth, like fire in timber, God is present but not patent in everything. God is in the human body and in the human mind. To become aware of Him there, spiritual effort is necessary. When that is undertaken, union with the Supreme within can be realised.