Surah Al Ma'idah Tafseer

ذَلِكَ أَدْنَى أَن يَأْتُواْ بِالشَّهَادَةِ عَلَى وَجْهِهَا

That should make it closer (to the fact) that their testimony would be in its true nature and shape (and thus accepted),

means, the ruling requiring the two Dhimmi witnesses to swear, if there is a doubt that they were not truthful, might compel them to admit to the testimony in its true form.

Allah's statement,

أَوْ يَخَافُواْ أَن تُرَدَّ أَيْمَانٌ بَعْدَ أَيْمَانِهِمْ

or else they would fear that (other) oaths would be admitted after their oaths.

means, requiring them to swear by Allah might encourage them to admit to the true testimony because they respect swearing by Allah and they glorify and revere Him. They also fear exposure if the heirs of the deceased are required to swear instead of them. In this case, the heirs would swear and earn the rightful inheritance that the two witnesses failed to declare. This is why Allah said,

(or else they would fear that (other) oaths would be admitted after their oaths).

then,

وَاتَّقُوا اللّهَ

And have Taqwa of Allah,

in all of your affairs,

وَاسْمَعُواْ

and listen,

and obey,

وَاللّهُ لَا يَهْدِي الْقَوْمَ الْفَاسِقِينَ

And Allah guides not the rebellious people.

who do not obey Him or follow His Law