Why Tagore called ‘Where the mind’ a prayer song?

This poem Where the Mind is without Fear is written in the form of prayer. The entire poem is a single complex sentence with several sub clauses starting with ‘where’ and the main clause, that is the prayer itself comes at the end – “Into that heaven of freedom, my father, let my country awake.”

Again, in its theme, the poem is a prayer song where Tagore prays to the God to raise his nation to the state of a ‘heaven of freedom’ where there would be no social evils like fear, ignorance, laziness, intolerance, disharmony, prejudices and such.

For a better understanding, read this summary of the poem.