Tafsir of Al-Anfal 8:55

{الذين كفروا فهم لا يؤمنون} They persisted in disbelief and remained obstinate in it, such that faith is not to be expected from them. These are the Banu Qurayza. The Messenger of Allah (ﷺ) made a covenant with them that they would not support anyone against him, but they broke it by aiding the polytheists of Mecca with weapons, claiming, "We forgot and we erred." Then he made a covenant with them again, and they broke it and sided with them on the Day of the Trench. Ka'b ibn al-Ashraf went to Mecca and formed an alliance with them.

{الذين عاهدت منهم} This is an appositive (badal) for "those who disbelieved." It means: those among the disbelievers whom you made a covenant with. He designated them as the worst of creatures because the worst of people are the disbelievers, the worst of the disbelievers are those who persist in it, and the worst of those who persist are those who break their covenants.

{وهم لا يتقون} They do not fear the consequences of treachery, nor do they care about the shame or the Fire that it entails.

{فإما تثقفنهم فى الحرب} If you encounter them and gain the upper hand over them in war.

{فشرد بهم من خلفهم} Disperse those behind them by killing them in the most severe manner and inflicting damage upon them, so that those behind them—the other disbelievers—are deterred. This is so that no one dares to oppose you after them, taking them as a lesson and a warning from their state.

Ibn Mas'ud (may Allah be pleased with him) read it as fashridh (with a dotted dhal), meaning "to scatter." It is as if it were a transposition of shadhara, from the saying "they went shadhara madhara." From this comes al-shadhar (scattered gold particles from a mine) due to their dispersion.

Abu Haywa read it as min khalfihim (from behind them). Its meaning is: perform the act of scattering upon those behind them. For when you scatter those who are behind them, you have performed the act of scattering in the rear and inflicted it upon it, because the "rear" is the direction of those being scattered. When the rear is made the location for the scattering, it indicates the scattering of those within it; thus, there is no difference between the two readings.

{لعلهم يذكرون} So that those behind them may take heed.

{وإما تخافن من قوم خيانة فانبذ إليهم على سوآء إن الله لا يحب الخائنين}