التفسير التبليغي
(They said, "O our father, indeed we went forth to race, and left Yusuf with our belongings, and the wolf devoured him. But you will not believe us, even if we should be truthful.") (17)
﴿نَسْتَبِقُ﴾ means we race each other.
﴿نَسْتَبِقُ﴾ means: we run on our feet to see who is faster.
﴿قَالُوا يَا أَبَانَا إِنَّا ذَهَبْنَا﴾, they immediately began narrating the fabricated reasons they had concocted, without hesitation or delay.
﴿يَا أَبَانَا﴾ is an appeal to the fatherly emotion.
He did not believe their claim and was not convinced by it.
He did not remain silent, because silence would encourage them to further fabrication and evil deeds..!
The intended meaning: racing by running on foot, which is part of the youthful exuberance and play.
Al-Mataa' (مَتَاعُ): what is enjoyed, meaning what is benefited from.
﴿قَالُوا يَا أَبَانَا إِنَّا ذَهَبْنَا نَسْتَبِقُ﴾ we race in running ﴿وَتَرَكْنَا يُوسُفَ عِنْدَ مَتَاعِنَا فَأَكَلَهُ الذِّئْبُ وَمَا أَنْتَ بِمُؤْمِنٍ لَنَا﴾ meaning you will not believe us ﴿وَلَوْ كُنَّا صَادِقِينَ﴾ due to your ill-suspicion of us and your excessive love for Yusuf.
﴿وَمَا أَنْتَ بِمُؤْمِنٍ لَنَا وَلَوْ كُنَّا صَادِقِينَ﴾, this is the kind of statement an apologizer makes when he runs out of reasons and all avenues of deception are closed to him.
﴿وَمَا أَنْتَ بِمُؤْمِنٍ لَنَا وَلَوْ كُنَّا صَادِقِينَ﴾, and they were not truthful!!
Whoever lies, no matter how much he tries to be clever and feign sadness, will inevitably stumble with his tongue and make slips in his speech.
Source: التفسير التبليغي