The Prophet's companions did not take as a starting date for the Muslim calendar, the day, the Prophet (ﷺ) had been sent as an Apostle or the day of his death, but the day of his arrival at Medina.

"When the Prophet (ﷺ) arrived at Medina, the eldest amongst his companions was Abu Bakr. He dyed his hair with Hinna and Katam till it became of dark red color.

The first people who came to us (in Medina) were Mus`ab bin `Umar and Ibn Um Maktum who were teaching Qur'an to the people. Then their came Bilal. Sa`d and `Ammar bin Yasir. After that `Umar bin Al-Khattab came along with twenty other companions of the Prophet. Later on the Prophet (ﷺ) himself (to Medina) and I had never seen the people of Medina so joyful as they were on the arrival of Allah's Apostle, for even the slave girls were saying, "Allah's Messenger (ﷺ) has arrived!" And before his arrival I had read the Sura starting with:-- "Glorify the Name of your Lord, the Most High" (87.1) together with other Suras of Al-Mufassal.

When Allah's Messenger (ﷺ) came to Medina, Abu Bakr and Bilal got fever, and I went to both of them and said, "O my father, how do you feel? O Bilal, how do you feel?" Whenever Abu Bakr's fever got worse, he would say, "Every man will meet his death once in one morning while he will be among his family, for death is really nearer to him than his leather shoe laces (to his feet)." And whenever fever deserted Bilal, he would say aloud, "Would that I know whether I shall spend a night in the valley (of Mecca) with Idhkhir and Jalil (i.e. kinds of grass) around me, and whether I shall drink one day the water of Mijannah, and whether I shall see once again the hills of Shamah and Tafil?" Then I went to Allah's Messenger (ﷺ) and told him of that. He said, "O Allah, make us love Medina as much as or more than we used to love Mecca, O Allah, make it healthy and bless its Sa' and Mud (i.e. measures), and take away its fever to Al-Juhfa."

During the last Hajj led by `Umar, `Abdur-Rahman bin `Auf returned to his family at Mina and met me there. `AbdurRahman said (to `Umar), "O chief of the believers! The season of Hajj is the season when there comes the scum of the people (besides the good amongst them), so I recommend that you should wait till you go back to Medina, for it is the place of Migration and Sunna (i.e. the Prophet's tradition), and there you will be able to refer the matter to the religious scholars and the nobles and the people of wise opinions." `Umar said, "I will speak of it in Medina on my very first sermon I will deliver there."

That he was sold (as a slave) by one master to another for more than ten times (i.e between 13 and 19).

The interval between Jesus and Muhammad was six hundred years.

Originally, two rak`at were prescribed in every prayer. When the Prophet (ﷺ) migrated (to Medina) four rak`at were enjoined, while the journey prayer remained unchanged(i.e. two rak`at).

The Prophet (ﷺ) said, "Had only ten Jews (amongst their chiefs) believe me, all the Jews would definitely have believed me."

When the Prophet (ﷺ) arrived at Medina, he noticed that some people among the Jews used to respect Ashura' (i.e. 10th of Muharram) and fast on it. The Prophet (ﷺ) then said, "We have more right to observe fast on this day." and ordered that fasting should be observed on it.

When the Prophet (ﷺ) arrived at Medina he found that the Jews observed fast on the day of 'Ashura'. They were asked the reason for the fast. They replied, "This is the day when Allah caused Moses and the children of Israel to have victory over Pharaoh, so we fast on this day as a sign of glorifying it." Allah's Messenger (ﷺ) said, "We are closer to Moses than you." Then he ordered that fasting on this day should be observed.

The Prophet (ﷺ) used to keep his hair falling loose while the pagans used to part their hair, and the People of the Scriptures used to keep their hair falling loose, and the Prophet (ﷺ) liked to follow the People of the Scriptures in matters about which he had not been instructed differently, but later on the Prophet (ﷺ) started parting his hair.

I am from Ram-Hurmuz (i.e. a Persian town).