The short answer is Pisidian Antioch and Syrian Antioch. Antioch of Syria, also known as Antioch on the Orontes River, was the third-largest city in the Roman Empire. Only Rome in Italy and Alexandria in Egypt were larger. Syrian Antioch (current-day Antakya, Turkey) was situated on the Orontes River about 20 miles inland from the Mediterranean Sea and approximately 300 miles north of Jerusalem. From its founding in 300 BC by Seleucus I Nicator, Syrian Antioch was a busy seaport trade hub possessing a mix of people from different cultures and religions with high intellectual and political status. Antioch of Syria played a significant role in the book of Acts and the earliest developments in the spread of Christianity. The city was home to many Diaspora Jews—those deported through captivity who had chosen to remain living outside Israel but maintain their Jewish faith. These Hebrews engaged in business and enjoyed full rights of citizenship in the free city of Syrian Antioch. Through them, many Gentiles in Antioch were drawn to Judaism and, eventually, Christianity.
The Syriac Orthodox Church, also called the Syrian Orthodox Patriarchate of Antioch and All the East, is a self-governing branch of Oriental Orthodoxy. The Syrian Orthodox Church is based in Damascus, Syria, and has vicariates in Australia, Germany, Netherlands, Sweden, the United Kingdom, Argentina, Brazil, Canada, the U.S., Turkey, Israel, and other countries. The Syriac Orthodox Church is in communion with the other five branches of the Oriental Orthodox Church but not with the churches of Eastern Orthodoxy. The Syriac Orthodox Church joined the World Council of Churches in 1960; according to the WCC, the Syriac Orthodox Church has about 1.4 million members worldwide. The Oriental Orthodox Church, of which the Syriac Orthodox Church is a part, differs from the Eastern Orthodox Church in that the Oriental Church recognizes only the first three ecumenical councils (Nicea, Constantinople, and Ephesus), whereas the Eastern Church recognizes all seven of the ecumenical church councils. Besides the Syriac Orthodox Church, Oriental Orthodoxy includes five other autonomous churches: the Coptic Orthodox Church of Alexandria (Egypt), the Ethiopian Orthodox Church, the Eritrean Orthodox Church, the Armenian Apostolic Church, and the Malankara (Indian) Orthodox Syrian Church. The Syriac Orthodox Church traces its history all the way back to Acts 11:26: “The disciples were called Christians first at Antioch.” The city of Antioch in this verse is Syrian Antioch, which later became the center of the Syriac Orthodox Church. The Syriac Orthodox Church claims that the apostle Peter founded the church and was its first bishop. At various times in history, the Syriac Orthodox Church was decimated by invasion of Mongols and Muslims.
The Syriac Orthodox Church, along with other Oriental Orthodox groups, separated from the rest of Christianity in AD 451 after the Council of Chalcedon. The sticking point for these groups was the nature of Christ. The Syriac Orthodox Church saw Chalcedon’s statement concerning Christ’s two unified natures (human and divine) as conceding too much to Nestorianism. The Syriac Orthodox Church and other non-Chalcedonian churches hold to the error of monophysitism(or miaphysitism), which views Christ as only having one nature. The Syriac Orthodox Church holds a liturgical worship service and uses the Peshitta as its text. The faithful pray seven times a day (based on Psalm 119:164), facing east, at specific times of the day. They observe seven sacraments: baptism, confirmation, Holy Eucharist, repentance, the priesthood, anointing of the sick, and marriage. Of these seven, they teach that four are essential for salvation: baptism, confirmation, repentance and the Eucharist.
Doctrinally, the Syriac Orthodox Church is off base. The Syrian Orthodox Church prays to Mary, the “Bearer of God”; venerates saints; prays for the dead; and teaches a salvation based on religious works. The Bible is clear that salvation is all of grace, apart from human works (Romans 11:6). God forgives our sin debt freely, for the sake of Christ (Luke 7:41–42; Romans 3:24). The Syriac Orthodox requirement of keeping the sacraments is “another” gospel in contridction with scripture (Galatians 1:6–9).