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.
These various oaths to be taken by the witnesses after the prayer (when you doubt their testimony) and the rejection of their testimony increases the likelihood that they will testify in the way required by the sacred law, without them distorting the facts deceitfully. Witnesses are more likely to give true testimony for fear that they will be disgraced if the heirs give conflicting testimony. Be mindful of Allah by not lying or being deceitful in your testimony and oath. Listen to what you are instructed to do and obey. Allah does not guide those who go against Him.