9:122
۞ وَمَا كَانَ ٱلْمُؤْمِنُونَ لِيَنفِرُوا۟ كَآفَّةًۭ ۚ فَلَوْلَا نَفَرَ مِن كُلِّ فِرْقَةٍۢ مِّنْهُمْ طَآئِفَةٌۭ لِّيَتَفَقَّهُوا۟ فِى ٱلدِّينِ وَلِيُنذِرُوا۟ قَوْمَهُمْ إِذَا رَجَعُوٓا۟ إِلَيْهِمْ لَعَلَّهُمْ يَحْذَرُونَ
And it is not for the believers to go forth [to battle] all at once. For there should separate from every division of them a group [remaining] to obtain understanding in the religion and warn their people when they return to them that they might be cautious.
Translation · Saheeh International
Tafsir
Ibn Kathīr (abridged)
Allah the Exalted here explains His order to Muslims to march forth with the Messenger of Allah ﷺ for the battle of Tabuk.
We should first mention that a group of the Salaf said that marching along with the Messenger ﷺ, when he went to battle, was at first obliged on all Muslims, because, as they say, Allah said,
انْفِرُواْ خِفَافًا وَثِقَالاً
(March forth, whether you are light or heavy) 9:41, and,
مَا كَانَ لأَهْلِ الْمَدِينَةِ وَمَنْ حَوْلَهُمْ مِّنَ الاٌّعْرَابِ
(It was not becoming of the people of Al-Madinah and the bedouins of the neighborhood...) 9:120. However, they said, Allah abrogated this ruling (9:41 and 9:120) when He revealed this Ayah, 9:122. However, we could say that this Ayah explains Allah's order to participate in battle on all Arab neighborhoods, that at least a group of every tribe should march for Jihad. Those who went with the Messenger ﷺ would gain instructions and studies in the revelation that came down to him, and warn their people about that battle when they returned to them. This way, the group that went with the Prophet will achieve both goals Jihad and learning the revelation from the Prophet . After the Prophet , a group of every tribe or neighborhood should seek religious knowledge or perform Jihad, for in this case, Jihad is required from at least a part of each Muslim community. `Ali bin Abi Talhah reported from Ibn `Abbas about the Ayah,