Tafsir of Al-An'am 6:51

{And warn by it those...}

The pronoun [in "by it"] refers to His saying: {and what is revealed to me}.

{Those who fear that they will be gathered}:

1. They are people who have entered Islam and affirm the Resurrection, but are negligent in their deeds; so he warns them by what is revealed to him, {that they may become righteous}, meaning: that they may enter into the group of the righteous among the Muslims.
2. Or, they are the People of the Book, because they affirm the Resurrection.
3. Or, they are people among the polytheists whose condition revealed that when they heard of the Resurrection, they feared it might be true and that they would perish. They are among those for whom it is hoped that the warning will be effective, unlike the rebellious among them; thus, he was commanded to warn these specific people.

{They have no protector or intercessor besides Him}: This is in the position of a hal (state) for [those who] {will be gathered}. It means: they fear that they will be gathered while being neither aided nor interceded for. This state is necessary, because everyone will be gathered; therefore, what is feared is specifically the gathering in this state.

{And do not drive away those who call upon their Lord morning and evening, seeking His countenance. Neither you are accountable for them in anything, nor are they accountable for you in anything, that you should drive them away and thus become of the wrongdoers.}