Tafsir of Al-Fath 48:16

{Say to those who remained behind} They are those who stayed behind from [the expedition of] al-Hudaybiyyah.

{To a people of great might} This refers to the Banu Hanifah, the people of Musaylimah, and the apostates whom Abu Bakr al-Siddiq (may Allah be pleased with him) fought. This is because the polytheists of the Arabs and the apostates are those from whom nothing is accepted except Islam or the sword, according to Abu Hanifah. As for others—the polytheists of the non-Arabs (Ajam), the People of the Book, and the Magians—the jizyah (poll tax) is accepted from them. According to al-Shafi‘i, the jizyah is not accepted except from the People of the Book and the Magians, excluding the polytheists of the non-Arabs and the Arabs.

This is evidence for the Imamate (leadership) of Abu Bakr al-Siddiq (may Allah be pleased with him), for they were not called to war during the days of the Messenger of Allah (peace be upon him), but rather after his passing. How could the Messenger of Allah (peace be upon him) have called them to war, given the Almighty’s saying: {Then say, "You will never go out with me, ever, and you will never fight an enemy with me"} (At-Tawbah: 83)?

It is also said: They are the Persians and the Byzantines. The meaning of {they submit} is "they yield," because the Byzantines are Christians and the Persians are Magians, from whom the payment of jizyah is accepted.

If you ask: Qatadah says they are the tribes of Thaqif and Hawazin, and that this occurred during the days of the Messenger of Allah (peace be upon him)? I reply: If that is authentic, then the meaning is: "You will never go out with me as long as you remain in your state of heart-disease and instability in religion." Or, according to Mujahid: The promise was that they would not follow the Messenger of Allah (peace be upon him) except as volunteers, with no share in the spoils of war.

{As you turned away before} Meaning, during the expedition of al-Hudaybiyyah.

{Or they submit} This is conjoined to {you fight them}. It means one of two things will occur: either fighting or submission; there is no third option. In the reading of Ubayy [ibn Ka‘b], it is (or until they submit).

{There is no blame upon the blind, nor is there blame upon the lame, nor is there blame upon the sick. And whoever obeys Allah and His Messenger, He will admit him to gardens beneath which rivers flow; but whoever turns away, He will punish him with a painful punishment.}