In OTL official Christianization of Rus started in the late X century. What if, instead of Christianity, Islam had been chosen?
From a contemporary perspective this would mean:
1st, a greater orientation toward the rising Islamic powers and it usually pays to be on victor's side. The existing trade relations with Byzantines and Italians would not suffer too much: the Muslim traders had been actively operating all the way to the Baltic coast and slave trade was a business too profitable to be destroyed by the doctrinal differences.
2nd, a lesser religious dependency from a foreign power. For quite a while Russian Church was a junior metropolitanate of the Patriarchate of Constantinople and the Ecumenical patriarch appointed the metropolitan, who usually was a Greek, who governed the Church of Rus. The 1st Russian bishop was installed by the Council of Russian bishops in Moscow as Metropolitan of Kiev and All Russia only in 1448 and Patriarchate of Moscow was created only in 1589. OTOH, a rather abstract dependency from a Caliph (with, more than once, an option to chose which one) meant a much greater freedom for the local princes.
3rd, polygamy would not have to be abolished.
4th, there would be a problem with drinking prohibition but, realistically, it never disappeared in the Islamic world and could be safely ignored. The important personages (if they cared), could get special permissions from the local spiritual authorities and the rest would just keep drinking.
A long term perspective.... could be interesting.
From a contemporary perspective this would mean:
1st, a greater orientation toward the rising Islamic powers and it usually pays to be on victor's side. The existing trade relations with Byzantines and Italians would not suffer too much: the Muslim traders had been actively operating all the way to the Baltic coast and slave trade was a business too profitable to be destroyed by the doctrinal differences.
2nd, a lesser religious dependency from a foreign power. For quite a while Russian Church was a junior metropolitanate of the Patriarchate of Constantinople and the Ecumenical patriarch appointed the metropolitan, who usually was a Greek, who governed the Church of Rus. The 1st Russian bishop was installed by the Council of Russian bishops in Moscow as Metropolitan of Kiev and All Russia only in 1448 and Patriarchate of Moscow was created only in 1589. OTOH, a rather abstract dependency from a Caliph (with, more than once, an option to chose which one) meant a much greater freedom for the local princes.
3rd, polygamy would not have to be abolished.
4th, there would be a problem with drinking prohibition but, realistically, it never disappeared in the Islamic world and could be safely ignored. The important personages (if they cared), could get special permissions from the local spiritual authorities and the rest would just keep drinking.
A long term perspective.... could be interesting.