Expression ei sy ei (if you are) in the Bible

(Translation from NRSV for the New Testament and Brenton for the Septuagint with a few modifications for a more literal meaning)

Matthew

14: 28Peter answered him, "Lord, if it is you (ei sy ei), command me to come to you on the water."
26: 63But Jesus was silent. Then the high priest said to him, "I put you under oath before the living God, tell us if you are (ei sy ei) the Messiah, the Son of God."

Luke

22: 67They said, "If you are (ei sy ei) the Messiah, tell us." He replied, "If I tell you, you will not believe;
23: 37and saying, "If you are (ei sy ei) the King of the Jews, save yourself!"

John

10: 24So the Jews gathered around him and said to him, "How long will you keep us in suspense? If you are (ei sy ei) the Messiah, tell us plainly."

Genesis (LXX)

27: 21And Isaac said to Jacob, Draw nigh to me, and I will feel thee, son, if thou art (ei sy ei) my son Esau or not.

Judges (LXX)

13: 11And Manoë arose and followed his wife, and came to the man, and said to him, Art thou (ei sy ei) the man that spoke to the woman? and the angel said, I am.

2 Samuel (LXX: 2 Kings)

2: 20And Abenner looked behind him, and said, Art thou (ei sy ei) Asael himself? and he said, I am.
9: 2And there was a servant of the house of Saul, and his name was Siba: and they call him to David; and the king said to him, Art thou (ei sy ei) Siba? and he said, I am thy servant.
20: 17And he drew nigh to her, and the woman said to him, Art thou (ei sy ei) Joab? and he said, I am. And she said to him, Hear the words of thy handmaid; and Joab said, I do hear.

1 Kings (LXX: 3 Kings)

13: 14and went after the man of God, and found him sitting under an oak: and he said to him, Art thou (ei sy ei) the man of God that came out of Juda? And he said to him, I am.
18: 7And Abdiu was alone in the way; and Eliu came alone to meet him: and Abdiu hasted, and fell upon his face, and said, My lord Eliu, art thou (ei sy ei) indeed he?
18: 17And it came to pass when Achaab saw Eliu, that Achaab said to Eliu, Art thou (ei sy ei) he that perverts Israel?
19: 2And Jezabel sent to Eliu, and said, If thou art (ei sy ei) Eliu and I am Jezabel, God do so to me, and more also, if I do not make thy life by this time to-morrow as the life of one of them.