Taberî states that the expression 'وما أنت بمصدق لنا' does not mean that Jacob's sons are accusing themselves of falsehood or that they are admitting their father will not believe them even if they speak the truth. According to him, the true meaning is that they are expressing that their father will not believe them because of his bad suspicion and doubt about them, even if they were truthful people. He also reports that in different narrations, the word 'بالغيب' is interpreted as matters of the unseen such as paradise and hell, or as the Qur'an.

قيل: ليس معنى ذلك بواحد منهما، وإنما معنى ذلك: وما أنت بمصدق لنا ولو كنا من أهل الصدق الذين لا يتهمون لسوء ظنك بنا، وتهمتك لنا

According to Zemahşerî, this expression is a statement made by the brothers to Jacob, containing an emphasis on trust and truthfulness; even if the brothers claim that they are truthful and trustworthy people, Jacob's mistrust and bad suspicion towards them will not change this situation.

ولو كنا عندك من أهل الصدق والثقة ، لشدة محبتك ليوسف ، فكيف وأنت سيء الظن بنا ، غير واثق بقولنا

According to this exegete, the concept of 'istibâk' in the verse can be explained in two different ways: first, a race of arrow shooting (Zeccâc's view), and second, showing who is faster by conducting a running race (Suddî and Mukâtil's view). Furthermore, in the context of the expression 'bimusaddikin', it is noted that the word faith has the meaning of confirmation in its linguistic root, while in Islamic jurisprudence custom it is specialized to mean confirmation of everything said by Allah and His Messenger. It is explained that Jacob's not confirming his sons is not based on them being liars, but on his accusing them because of his excessive love for Joseph.

واختلفوا في معنى الاستباق قال الزجاج : يسابق بعضهم بعضا في الرمي ، ومنه قوله عليه الصلاة والسلام : ( لا سبق إلا في خف أو نصل أو حافر ) يعني بالنصل الرمي

According to Kurtubî, the brothers' statement 'racing and leaving our possessions behind' means guarding cloth and their possessions. This situation arose after they heard their father's statement 'I fear the wolf will eat him'; they took this statement from their father's mouth and tried to protect themselves with this expression, because the wolf danger was the most obvious fear in appearance.

وذلك أنهم لما سمعوا أباهم يقول : وأخاف أن يأكله الذئب أخذوا ذلك من فيه فتحرموا به لأنه كان أظهر المخاوف عليه

Ibn Kesîr points out that there is a subtle trap and psychological strategy in the words that Joseph's brothers spoke to their father. Although the brothers knew that their father would not believe them, they tried to convince him by emphasizing that this disbelief could be excused because of the strangeness of the event. In other words, they tried to justify Jacob's suspicion by the fact that the event was truly surprising.

تلطف عظيم في تقرير ما يحاولونه يقولون ونحن نعلم أنك لا تصدقنا والحالة هذه لو كنا عندك صادقين فكيف وأنت تتهمنا في ذلك لأنك خشيت أن يأكله الذئب فأكله الذئب فأنت معذور في تكذيبك لنا لغرابة ما وقع وعجيب مااتفق لنا في أمرنا هذا

Beydâvî explains that the brothers came to their father in the evening, weeping, saying that they left Joseph with their possessions and went to race, and that the wolf ate him. According to him, their father will not believe them, even if they speak the truth, because of his bad suspicion and excessive love for Joseph.

وما أنت بمؤمن لنا بمصدق لنا ولو كنا صادقين لسوء ظنك بنا وفرط محبتك ليوسف