He said, "I passed the examination long ago". (Change into indirect speech).

He said I passed the examination.

He said that he had passed the examination long before.

He said he had passed the examination long before.

He asked that he has passed the examination long before.

In indirect speech, we change the original sentence from "I passed the examination long ago" to "he had passed the examination long before".

Because "long ago" refers to a time in the past, which becomes "long before" in indirect speech.

Also, the pronoun "I" changes to "he" to match the subject of the sentence.