It is not surprising to find the word “amen” attributed to Jesus in the Gospels. “Amen” appears elsewhere in the New Testament, notably in the epistles of Paul, who usually used it to conclude an expression of praise to God. Nor is it odd that “amen” was simply transliterated from Hebrew into Greek. Its use had become so common in Greek-speaking synagogues and churches that the New Testament writers generally felt translation unnecessary. What is unusual is to find “amen” used as the beginning of a statement rather than as a response.
One may contend that there existed a basic text of Jesus’ life story written in Hebrew. One arrives at this assumption not merely on the basis of the church fathers’ writings, but because the Greek texts of the synoptic gospels show so much evidence of being “translation Greek,” that is, Greek that contains Hebrew idioms and sentence structures.