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.