Translation:

49. They said: "Swear a mutual oath by Allah that we shall make a secret night attack on him and his people and that we shall then say to his heir (when he seeks vengeance): `We were not present at the slaughter of his people and we are positively telling the truth.' "

Notes (Tafseer)

3287. A most dastardly plot, because (1) it was to be secret, (2) by night, (3) taking their victims unawares, and (4) because careful provision was made that they should all tell lies together, saying that they knew nothing about it, in order to evade the vengeance which Salih's heirs (if any were left) or his tribe might want to exact! And yet such were exactly the plots laid against the holy Prophet himself.