121.)] When Heraclius returned in triumph from the Persian war, he entertained, at Emesa, one of the ambassadors of Mahomet, who invited the princes and nations of the earth to the profession of Islam.

On this foundation the zeal of the Arabians has supposed the secret conversion of the Christian emperor: the vanity of the Greeks has feigned a personal visit of the prince of Medina, who accepted from the royal bounty a rich domain, and a secure retreat, in the province of Syria.

[145] But the friendship of Heraclius and Mahomet was of short continuance: the new religion had inflamed rather than assuaged the rapacious spirit of the Saracens, and the murder of an envoy afforded a decent pretence for invading, with three thousand soldiers, the territory of Palestine, that extends to the eastward of the Jordan.

The holy banner was intrusted to Zeid; and such was the discipline or enthusiasm of the rising sect, that the noblest chiefs served without reluctance under the slave of the prophet.

On the event of his decease, Jaafar and Abdallah were successively substituted to the command; and if the three should perish in the war, the troops were authorized to elect their general.