Sunan Abi Dawud 2761
سنن أبي داود#2761SahihNarrated Nu'aym ibn Mas'ud: I heard the Messenger of Allah (ﷺ) say when they (messengers sent by Musaylimah) read the letter of Musaylimah: What do you believe yourselves? They said: We believe as he believes. He said: I swear by Allah that were it not that messengers are not killed, I would cut off your heads
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautHasan
Zubair Ali ZaiIsnaad Hasan
In-book reference: 15:285