Muslims migrated twice to Habshah (Abyssinia) first in 613 CE and second in 616 CE to flee from the persecutions of Qureysh. First Migration comprised of eleven men and four women, the Second Migration comprised of eighty three men and fourteen women.

According to the traditional view, members of the early Muslim community in Mecca faced persecution, which prompted Muhammad to advise them to seek refuge in Abyssinia. According to Muslims historians, there were two migrations, although there are differences of opinion with respect to the dates.

circa 614 CE

The monarch (An-Naǧāshī) who ruled the Kingdom of Aksum at the time of the Hegira, was king Armah or As-hamah (أصحمة‎). The silver coin with the depiction of king Armah, minted during his reign. It has also been suggested that either he or probably his father, gave shelter to the Muslim emigrants around 615–6 CE at Axum. Although the Aksumite monarch who received them is known in Islamic sources as the Negus (نجاشي‎ najāšī) Ashama ibn Abjar. A historic mosque in Negash, the Najashi Masjid may have been named in his honour.

circa 614 CE

Migrants
The first group of Muslim emigrants that arrived in Aksum, comprised of twelve men and four women, was granted asylum in the year 7 (BHj.) (613 CE) under Ashama ibn-Abjar, the ruler of the Kingdom of Aksum. This group included Uthman ibn Affan, who later became the third caliph. This group reached Aksum, traveling via a ship from the sea port of Shuaiba, landing most probably at Adulis and then on to Aksum.

circa 614 CE

Route of First Migration
How did the Muslim migrants from Mecca traveled to Aksum, the details of their travels are very scant in historical sources. Ibn Sa'd relates in his book Kitab Tabaqat Al-Kubra on the authority of Harith ibn al-Fudail that the group boarded one of the two merchant ships from Shuaiba (Yaqut says it was the place where ships (marfa') used to beach for Mecca in the days before Jidda became its port), and paid half Dinar (دينار) each for faring them across the sea.

circa 614 CE

Abyssinia At the Time
At the time of Hijrah towards Habshah (Abyssinia), the Kingdom of Aksum was entering in a period of decline, known as the end of second goldan age of Aksumite Kingdom. This era of revival of the Aksumite power and it's decline conincides with the advent of Islam on the Arabian peninsula. So essentially when the Muslim migrants fleeing Mecca arrived in Aksum they would have found a relatively prosperous land. At the time the Kingdom of Aksum was a Christian majority land.

circa 615 CE

The second migration took place in 615 CE. The group of emigrants this time comprised eighty three men and eighteen to nineteen women. Following the first migration to Abyssinia, the Meccan polytheists were on the alert for a second migration, however they were not able to stop the Muslims' escape. During this period were the Muslims in Arabia subjected to the Meccan boycott of the Hashemites (617 CE), the Year of Sorrow (619 CE), Muhammad's visit to Ta'if (620), the Isra and Mi'raj (621 CE) and finally the Migration to Medina (622 CE).

circa 615 CE

The Kingdom of Aksum was declared as a favoured land by prophet Muhammad, if you have to migrate, migrate towards Habshah. The route of the Second Migration was most probably same as that of First Migration to Habshah (Abyssinia). The group left Mecca and headed towards the Shuaiba port, where they boarded a ship to cross the Red Sea. The only difference was the return route, Muslims returned to Medina rather than Mecca.

circa 614 CE

After the two migrantions some of the muslims settled in Habashah, possibly in Negash, some migrated and left Abyssinia by sea for preaching overseas to east Asia. According to an Islamic tradition as-Sahabah Mosque is the oldest mosque built in Eritrea by the first Muslim Migrants when they first arrived and settled in Abyssinia. This makes this Mosque the first in Africa.

There's another tradition, if we can trust the sources, which states that some early Muslim migrants may have traveled through or settled in Saylac (Somalia) as well.

Another notable event during the stay in Abyssinia is the marriage of Umm Habibah to the prophet Muhammad, around 628 CE. The marriage ceremony took place in Abyssinia even though Muhammad was not present. The Negus (king) of Abyssinia read out the Khutba himself, and Khalid ibn Said made a speech in reply. The Negus gave Khalid a dower of 400 dinars and hosted a huge wedding feast after the ceremony. He also sent musk and ambergris to the bride through the slave Barrah.