‘Amr b. Shu'aib, on his father’s authority, told that his grandfather reported God’s Messenger as saying in the course of his sermon, "Observe fully the alliance made in the pre-Islamic period, for it, i.e. Islam, will only make it stronger; but make no new alliances in Islam.”
Nu'aim b. Mas'ud reported God's Messenger as saying to two men who came from Musailima, "I swear by God that were it not that messengers are not killed, I would cut off your heads.”
Ibn Mas'ud told that when Ibn an-Nawwaha and Ibn Uthal, Musailima’s messengers, came to the Prophet he asked them whether they testified that he was God’s Messenger. On their replying, "We testify that Musailima is God’s messenger,” he said, "I believe in God and His Messenger. If it was my custom to kill a messenger I would kill you.” ‘Abdallah (i.e. Ibn Mas'ud) said that the sunna that a messenger should not be killed then came into force.
Quraish sent me to God’s Messenger and when I saw him Islam was cast into my heart, so I said, "Messenger of God, I swear by God that I shall never return to them.” He replied, "I do not break a covenant or imprison messengers; but return, and if you feel the same as you do just now, come back.” So I went away and then came to the Prophet and accepted Islam.
