Who is the actual doer according to the Gita?

From Sushant Kulkarni

Krishna says in the Gita: “Never consider yourself to be the cause of the results of your activities.” (2.47)
If we are not the cause of the fruit of our work then what is the cause of the fruit of our work? Is it only the material nature as mentioned in the verse 5.14, or is it all the five factors of action collectively as mentioned in the verse 18.14?