Tafsir of Al-Baqarah 2:208-209

"O you who have believed, enter into al-silm (peace/submission) entirely..."

[Al-Silm] Read with a kasra (i) or a fatha (a) on the sin. Al-A‘mash read it with a fatha on both the sin and the lam. It means submission and obedience. That is: submit to Allah and obey Him.

[Entirely (Kāffatan)] Let no one among you withdraw their hand from His obedience. It is also said that it means Islam, and the address is directed to the People of the Scripture—because they believed in their prophet and their book—or to the hypocrites, because they believed with their tongues. It is also permissible for kāffatan to be a state (ḥāl) of al-silm, as it is treated as feminine, just as al-ḥarb (war) is treated as feminine.

The poet said: "Peace—take from it what you are content with, And war—a few of its breaths are enough for you."

It implies that the believers are commanded to enter into all acts of obedience, not to enter into some and neglect others, or to enter into all the branches and laws of Islam without omitting any part of them.

Regarding ‘Abdullah ibn Salam: It is narrated that he asked the Messenger of Allah (ﷺ) for permission to continue observing the Sabbath and to recite from the Torah in his night prayers.

[Kāffatan] Derived from al-kaff (to restrain/withhold), as if they are restrained from anyone among them leaving the group by their collective unity.

"But if you slip..." ...away from entering into al-silm...

"...after the clear proofs have come to you..." ...meaning the arguments and evidence that what you have been called to enter is the Truth...

"...then know that Allah is Exalted in Might..." ...the Overpowering, whom nothing can prevent from taking retribution against you.

"...Wise." He does not take retribution except with justice.

It is narrated that a reciter read "Forgiving, Merciful" (Ghafūr Raḥīm) in place of "Exalted in Might, Wise." A Bedouin heard him, disapproved of it, and said, "If this were the word of Allah, He would not say that. The Wise One does not mention forgiveness after a slip, for that would be an encouragement to sin."

Abu al-Summal read zalaltum with a kasra on the lam. Both are linguistic variants, like ẓaliltu and ẓalaltu.

"Do they await but that Allah should come to them in covers of clouds and the angels [as well] and the matter is decided? And to Allah [all] matters are returned."