Tafsir of Al-Ahzab 33:70

(O you who have believed, fear Allah) in everything you do and leave, especially in committing what He, the Exalted, dislikes, let alone what harms His Messenger and beloved, may Allah's peace and blessings be upon him, (and speak) in every matter of affairs, (a word that is sadid [right and appropriate])—aiming for and directed toward the target of the truth. It is derived from sadad (to aim correctly); it is said, "He saddada (directed) his arrow," when he aims it at the target and does not deviate from its path.

The intended meaning, as it has been said, is to forbid them from the opposite of this speech, which is speech that is not sadid. Included in this is what emanated from them in the story of Zaynab, which was speech that deviated from justice and the intended goal, as well as any speech that harms him, peace and blessings be upon him.

According to Muqatil and Qatadah, the meaning is: "And speak a sadid word" regarding the affair of the Messenger, peace and blessings be upon him, Zayd, and Zaynab.

According to Ibn Abbas and Ikrimah, the sadid word is specifically La ilaha illa Allah (There is no god but Allah). It is also said: It is that whose outward appearance conforms to its inward reality. It is also said: It is that which contains rectification. Perhaps what we have indicated is most worthy.