Saf ibn Sayyad was an alleged claimant of prophethood during the time of Muhammad

Muhammad

Muhammad |ligature]] at U+FDF4 ;Arabic pronunciation varies regionally; the first vowel ranges from ~~; the second and the last vowel: ~~~. There are dialects which have no stress. In Egypt, it is pronounced not in religious contexts...

 and his companions

Sahabah

In Islam, the ' were the companions, disciples, scribes and family of the Islamic prophet...

.

Claims of prophethood in childhood

He claimed he was a prophet when he was on the threshold of adolescence, and was initially believed to be the False Messiah

False messiah

-Judaism:Armilus is an anti-Messiah figure in late-period Jewish eschatology, comparable to the Christian Antichrist and Muslim Dajjal, who will conquer Jerusalem and persecute the Jews until his final defeat at the hands of God or the true Messiah...

 (Dajjal), as his characteristics were the same as those of the False Messiah:

It was narrated that Muhammad met Ibn Sayyad, at that time Ibn Sayyad was just at the threshold of adolescence. Muhammad said: "Don't you bear testimony to the fact that I am the Messenger of Allah?" Ibn Sayyad he said: "No, but you should bear testimony that I am the messenger of Allah." Thereupon `Umar ibn Khattab

Umar

`Umar ibn al-Khattāb c. 2 November , was a leading companion and adviser to the Islamic prophet Muhammad who later became the second Muslim Caliph after Muhammad's death....

 said: "Allah's Messenger, permit me that I should kill him." Thereupon Muhammad said: "If he is that person who is in your mind Dajjal, you will not be able to kill him."

Characteristics

His characteristics were similar to those believed to be of the False Messiah:

Nafi' reported that `Abd Allah ibn `Umar

`Abd Allah ibn `Umar

Abdullah ibn Umar was the son of the second Caliph Umar ibn Khattab. He was a prominent authority in hadith and law, and was known for his neutrality toward factions engaged in the first civil war within the Muslim community ....

 met Ibn Sa'id on some of the paths of Medina and he said to him a word which enraged him and he was so much swollen with anger that the way was blocked. Ibn `Umar went to Hafsa bint Umar

Hafsa bint Umar

Ḥafsah bint ‘Umar and wife of the Islamic prophet Muhammad, and therefore a Mother of the Believers.-Biography:She was married to Khunais ibn Hudhaifa, but became a widow when she was eighteen and according to Islamic tradition her father offered her to Abu Bakr and Uthman Ibn Affan...

 and informed her about this. Thereupon she said: May Allah have mercy upon you, why did you incite Ibn Sayyad in spite of the fact that you knew it would be the extreme anger which would make Dajjal appear in the world?

Denial of being the Dajjal in adulthood

In adulthood he repented and embraced Islam:

Nafi' reported that Ibn `Umar met Ibn Sayyad (now known as Abdullah ibn Sa'id) and said to some of his friends: "You state that it was he (the Dajjal)." Ibn Sa'id said: "By Allah, it is not so". Ibn `Umar said: "You have not told me the truth; by Allah some of you informed me that he would not die until he would have the largest number of offspring and huge wealth and it is he about whom it is thought so."

Abu Sa`id al-Khudri reported: Ibn Sa'id said: "What I have gathered from people is that theu think that I am Dajjal. Has Muhammad not said that he would be an Kafir whereas I am a Muslim and he also said that he would not have children, whereas I have children, and he also said: verily, Allah has prohibited him to enter Mecca whereas I have performed Pilgrimage." He also said: "I know his place of birth his abode where he is just now."