Persian conquests. Four years after the proclamation of the mission of the Holy Prophet, war broke out between the Persians and the Byzantines. The sympathies of the Quraish of Makkah was with the Persians who were polytheists. The Muslims on the other hand had their sympathies for the Byzantines who were Christians and believed in one God. In the war the Persians overran the Byzantine territories. Syria and Jerusalem fell to Persians in 614 C.E. The Persians next marched to Egypt and annexed it 616 C.E The Byzantines were defeated, and lost a good deal of territory. The Quraish of Makkah rejoiced at the victory of Persia. They took such victory to signify that their gods were superior to the God of the Christians arid the Muslims.
Surah Ar-Rum. It was at this stage that the Surah Ar-Rum (Surah XXX) was revealed. It provided: “Alif, Lam Mim. The Greeks (Byzantines) have been defeated in a neighboring land; But after their defeat, they will gain a victory within a few years Allah’s is the command before and after. On the day that the Greeks win a victory, The believers will rejoice. Allah gives victory to whom He wills, He is the Mighty One, the Merciful. That is Allah’s promise. His promise can never be untrue; yet most men do not know it.”
Reaction of the Quraish. When the Holy Prophet informed his companions of the revelation, they felt very happy. When the revelation was made, the Byzantines lay low, and prima facie appeared difficult that the Byzantines would defeat the Persians and regain their territories. Even among the Muslims there were some persons who felt skeptic. Abu Bakr’s faith know no wavering. He felt confident that the prophesy would be fulfilled. When the unbelievers came to know of this revelation they ridiculed it. They said, “By Lat and Uzza, the Byzantines can never defeat the Persians.” Abu Bakr had an altercation with some of the Quraish. He said “How can the revelation of God be false?”
The Wager. Ubaiy b Khalf a Quraish leader said to Abu Bakr, “If you are sure, let us have a wager. That will show where the truth lies.” Abu Bakr said “Agreed”. The revealed verses did not specify any time limit about the fulfillment of the prophesy. Abu Bakr consulted the Holy Prophet as to the time limit and he said that God willing the prophesy would be fulfilled within nine years. Abu Bakr accordingly entered into a wager agreement with Ubaiy b. Khalf. According to the agreement it was stipulated that the party which lost the wager would pay one hundred camels to the other party. The time limit for the fulfillment of the prophesy was fixed at nine years. It was further laid down that the agreement would be binding on the heirs of the parties.
Fulfillment of the prophesy. Within a few years the Byzantines were strong enough to launch an attack against Persia. In the battle of Issus in 622 C.E. the Persians suffered the first defeat. Other battles were fought during 623-25 in which the Byzantines had the upper hand. The decisive battle was fought on the banks of the Tigris near the city of Mosul in 627 C.E. when Persia surrendered and asked for terms. As a result of this reverse there was a revolt against the Persian king Khosroes II who was killed by his own son Sherwayh. Sherwayh made peace with the Byzantines by abandoning all the conquests that Persia had made earlier. Thus the promise of God as made in Surah Ar-Rum was literally fulfilled. By this time Ubaiy was dead, but his heirs honored the agreement and gave a hundred camels to Abu Bakr!
They also accepted Islam, for the fulfillment of the prophesy was a proof positive of the truth of Islam. Abu Bakr gave away all the hundred camels as Sadaqa
Source : Hadrat Abu Bakr, Umar, Usman, Ali (ra) 4 Vol. Set