Several historical evidences shed light on a significant Malankara–Persian ecclesiastical relationship that spanned centuries. While an ecclesiastical relationship existed between the Saint Thomas Christians of India and the Church in Sassanid Empire (Church of the East) in the earlier centuries, closer ecclesiastical ties developed as early as seventh century, when India became an ecclesiastical province of the Church of the East, albeit restricted to matters of purely ecclesiastical nature such as ordination of priests, and not involved in matters of temporal administration. This relationship endured until the Portuguese protectorate of Cochin of Malabar came to be in 16th century, and the Portuguese discovery of a sea route to India. The Christians who came under the two ancient yet distinct lineages of Malankara and Persia had one factor in common: their Saint Thomas heritage. The Church of the East shared communion with the Great Church (Catholicism, Eastern Orthodoxy and Oriental Orthodoxy) until the Council of Ephesus in the 5th century, separating primarily over differences in Christology.
The Saint Thomas Christians of India came in contact with Portuguese Latin Catholic missionaries only in the 16th century. Later, after the Oath of Koonan Cross (meaning "leaning cross") in 1653, the Saint Thomas Christians came in touch with the Syriac Orthodox Church.
Though claims have been made that the Saint Thomas Christians of Malankara had close interactions with the Roman Catholic Church and Syriac Orthodox Church before the 16th century, these assertions lack proof.
Early references
The celebrated Church historian Eusebius has mentioned in his work that the Alexandrian scholar Pantenus had seen Christians during his visit to India between 180 A. D. and 190 A. D. This account of Eusebius has later been quoted by several historians. According to Eusebius, Pantenus saw people reading the Gospel according to Mathew in Hebrew. Based on this reference by Eusebius, Jerome has recorded the existence of Christians in India during the early centuries of Christian Era. In addition to this, Jerome mentions that Pantenus held debates with Brahmins and philosophers in India.
The evangelization of India is mentioned in a number of ancient works, including the book Acts of Judas Thomas written in Edessa around 180 A. D. in Syriac language, and Didascalia (meaning teachings of the Apostles) written around 250 A. D. Historians have often remarked that the Persians might have received this tradition about the Church in India from India itself.
The Chronicle of Seert is a historical document compiled in the Middle Ages. In this Chronicle, the Church in India is mentioned along with the history of Persian Church and the Patriarchs (Catholicoi) of Babylon. It also states that during the reigns of Shahlufa and Papa bar Aggai as the heads of Persian Church, the Persian bishop David of Basra preached the Gospel in India. Some historians' records regarding the participation of Bishop John representing Persia and India as the Bishop of all of Persia and Greater India in the first Ecumenical Council of Nicaea in 325 A. D. remains a matter of contention among historians.
Ishodad was a famous Bible scholar who lived in Persia in the 5th century. In his commentary on the Epistle to Romans, a note is scribbled in the margin that may be translated as: This article is translated by Mar Komai with the help of Daniel, an Indian priest, from Greek to Syriac. This statement reveals the connection between the Indian priest Daniel and the Persian bishop Mar Komai.
Persian Immigration
The two instances of immigration from Persia to Malankara (India) substantiate the Malankara-Persia connection. The first of these, which occurred in the 4th century, was led by a merchant named Thoma (fondly referred to as Knai Thoma or Knai Thomman by the Christians of Malankara, meaning Thomas of Cana), while the second immigration was led by two Persian bishops, Prod and Sappor in the 9th century.
There exists the strong traditional belief that Thomas of Cana, accompanied by a Persian bishop and seventy two families, reached the ancient port of Kodungallur in India. The history of Knanaya in Malankara is inseparably related to this immigration.