They swear by Allah that they said nothing, but they definitely spoke the word of kufr and returned to kufr after their Islam. They planned something which they did not achieve and they were vindictive for no other reason than that Allah and His Messenger had enriched them from His bounty. If they were to make tawba, it would be better for them. But if they turn away, Allah will punish them with a painful punishment in this world and the Next World, and they will not find any protector or helper on the earth.