Quran 5:106 — The Feast (Al-Ma'edah)

O you who believe, witnessing a will when one of you is dying shall be done by two equitable people among you. If you are traveling, then two others may do the witnessing. After observing the Contact Prayer (Salat), let the witnesses swear by GOD, to alleviate your doubts: "We will not use this to attain personal gains, even if the testator is related to us. Nor will we conceal GOD's testimony. Otherwise, we would be sinners."

[5:105] O you who believe, you should worry only about your own necks. If the others go astray, they cannot hurt you, as long as you are guided. To GOD is your ultimate destiny, all of you, then He will inform you of everything you had done.

[5:107] If the witnesses are found to be guilty of bias, then two others shall be asked to take their places. Choose two persons who were victimized by the first witnesses, and let them swear by GOD: "Our testimony is more truthful than theirs; we will not be biased. Otherwise, we will be transgressors."