He is a teacher in a village whose people gave him some olive oil, and he does not know whether it was zakaah or a gift

Firstly: 

Gifts from the people of the village to the teacher are subject to further discussion: 

1.If the gifts are given by people who have children who are his students, he does not have the right to accept it, because usually that will make him more inclined to the one who gave him a gift and he will not be fair between that person’s children and the other students. See the answer to question no. 82386

2.If it comes from a person who does not have any children in school or it comes from all the people of the village as a way of honouring the teacher because he is a guest in their village – as is the case in some areas – and that will not affect his work or his relationship with his students, then there is nothing wrong with accepting it.

Secondly: 

If the matter has to do with determining whether what you were given was zakaah or a gift, do you have to ask about that? This is also subject to further discussion: 

1.If you are qualified to receive zakaah and accepting the gift in this case was permissible, there is nothing wrong with you accepting what is given to you and you do not have to ask and find out about it.

2.If you are not qualified to receive it in either case, then it is not permissible for you to accept it, but you should be kind and gentle in refusing it, so that this will not spoil the relationship between you and the people of the village.

3.If you are qualified to receive zakaah but not gifts, or vice versa, then you should ask and find out so that you will know what is permissible for you to accept and what is not permissible.

And Allah knows best.