Fear Allah in All Your Affairs
In this ayah Allah subhanahu wa ta’ala elucidates the benefit of testimony by the heirs of the deceased against the two witnesses.
ذلِكَ أَدْنَى أَن يَأْتُواْ بِالشَّهَـدَةِ عَلَى وَجْهِهَآ أَوْ يَخَـفُواْ أَن تُرَدَّ أَيْمَـنٌ بَعْدَ أَيْمَـنِهِمْ وَاتَّقُوا اللَّهَ وَاسْمَعُواْ وَاللَّهُ لاَ يَهْدِى الْقَوْمَ الْفَـسِقِينَ
“That should make it closer (to the fact) that their testimony would be in its true nature and shape, or else they would fear that (other) oaths would be admitted after their oaths. And have Taqwa of Allah and listen (with obedience to Him). And Allah guides not the rebellious people.”
The word wajhiha is from the root letters wau-jeem-ha. Wajh means “face”. Face denotes something that’s obvious.
When the two witnesses know that two heirs from the deceased’s side can come and give a testimony against them, they will be conscious of what they are saying. This fear will compel them to say the truth and handover whatever belongings of the deceased they have in their possession.
Allah subhanahu wa ta’ala ends this ayah by saying fear Allah in all of your affairs and listen attentively or obey. Allah does not guide those who are rebellious i.e. those who do not obey and follow His law.
[SOURCE: Tafseer Ibn Katheer]