It is narrated from Hazrat Safwan bin Amr, may Allah have mercy on him: The Romans imprisoned their king, Istiban al-Ahzam, and confined him to an island. Some merchants recognized him and took him to Hauran. He sought refuge with Muhammad bin Marwan and said: "Allow me to pass through your land to return to Rome." Muhammad sought permission from Abdul Malik bin Marwan. Istiban promised that if Allah restored his rule, he would free any Muslim found in Rome praying facing the Qiblah. With the help of the Muslims, he prevailed over Rome, freed the Muslims, brought them to Qinnasrin, and gave them five dinars each. Abdul Malik and the Muslims were pleased with this.
Hadith Referenceسنن سعید بن منصور / كتاب الجهاد / 4097