Al-Quran

*We will soon show them Our signs in the Universe and in their own souls until it will become quite clear to them that it is the truth. Is it not sufficient as regards your Lord that He is a witness over all things?41:53

Worship Allah as if you can see Him,...

The Prophet (peace be upon him) said: "Worship Allah as if you can see Him, even though you cannot see Him, He can see you." [Muslim]