Al-Ma'idah 5:108

Thalika adna an ya/too bishshahadatiAAala wajhiha aw yakhafoo an turadda aymanunbaAAda aymanihim wattaqoo Allaha wasmaAAoowallahu la yahdee alqawma alfasiqeen

That is more likely that they will give testimony according to its [true] objective, or [at least] they would fear that [other] oaths might be taken after their oaths. And fear Allāh and listen [i.e., obey Him]; and Allāh does not guide the defiantly disobedient people.

Thus, it is more likely that the former people (i.e. the executors of the bequest) will bear witness in its proper way, or they will fear that oaths will be taken in rebuttal of their oaths. Fear Allah and listen. Allah does not lead sinning people to the right path.