al-Kāfi: And from him, from a number of our companions, from Aḥmed bin Moḥammed al-Barqi, from al-Qāasim bin Yaḥya, from his grandfather al-Ḥassan ibn Rāshid:

From Abī al-Ḥassan Mūsa bin Jaʿfar عليه السلام, who said: He [al-Kādhum] was asked about the meaning of Allāh.
He replied: He has authority over what is minute and what is grand.1

1. Here the Imām عليه السلام explains the meaning of Allāh by stating that His authority embraces everything, even:
a) that which is minute (i.e. small) – even that which cannot be seen by the naked eye, like atoms, which can only be seen by a microscope.
b) that which is grand (i.e. big) – such as the planets and galaxies.
In other words there’s nothing that is outside His authority and power as the Qur’ān states many times: ‘Indeed Allah is over all things powerful’.

وعنه : عن عدة من أصحابنا ، عن أحمد بن محمد البرقي ، عن القاسم بن يحيى ، عن جده الحسن ابن راشد ، عن أبي الحسن موسى بن جعفر ( عليه السلام ) قال : سئل عن معنى الله ، فقال : استولى على ما دق وجل