What is the ruling on someone who drank alcohol without knowing it was alcohol?

If someone drank alcohol unknowingly that it was alcohol, and did not act negligently, then he is excused and there is no sin upon him. This is based on the Almighty's saying: "Our Lord, do not take us to task if we forget or make a mistake," and on the Prophet, peace and blessings be upon him, saying: "Lifted from my Ummah are mistakes, forgetfulness, and what they are coerced into."