A grammatical point

Today, we celebrate the Feast of St. Paul's Conversion. The story is recorded in Acts 9. As a matter of literary interest, the story on the road to Damascus was told three times in Acts 9, 22 and 26. It would be a worthwhile exercise for Bible students (including me) to do a comparison and speculate why Luke told the same story three times, in different occasions, to the audience. Moreover, Paul's own testimony in Galatians 1:15-19 was different from that in Acts. Of course, it would be challenging and interesting to harmonize them.
Some scholars claim that Christianity was fathered by Paul rather than Jesus. They argued that the New Testament contains far more materials attributed to Paul than to Jesus. There are 14 epistles authored by Paul but only 4 canonical gospels. I use 'authored' instead of 'written' because scholars argue that only 7 were written by Paul. The rest only has the authority of Paul behind them. Well, I will leave the subtlety of arguments to biblical scholars. As for me, Jesus is my Christ, my Saviour and this is enough.
Tonight in the Hebrew lesson, I was able to read Exodus 3:6. This passage was quoted by Jesus to prove that the Sadducees were wrong in trying to prove that there is no resurrection (Mark 12:26-27). Of course, Mark was written in Greek and Exodus in Hebrew. Septuagint is the most likely link.
Ἐγὼ ὁ θεὸς Ἀβραὰμ καὶ [ὁ] θεὸς Ἰσαὰκ καὶ [ὁ] θεὸς Ἰακώβ;  (Mark 12:26)
Ἐγώ εἰμι ὁ θεὸς τοῦ πατρός σου, θεὸς Αβρααμ καὶ θεὸς Ισαακ καὶ θεὸς Ιακωβ.(Septuagint)

(BHS)אָנֹכִי֙ אֱלֹהֵ֣י אָבִ֔יךָ אֱלֹהֵ֧י אַבְרָהָ֛ם אֱלֹהֵ֥י יִצְחָ֖ק וֵאלֹהֵ֣י יַעֲקֹ֑ב

Jacob, and God of,  Isaac, God of,  Abraham, God of, your father, God of,  I   

Hebrew is read from right to left and the verb to be is usually omitted.
Ἐγώ is the first person singular pronoun, meaning I. εἰμι is the verb to be in present tense.  Therefore, Ἐγώ εἰμι means 'I am'. Septuagint adds an 'am' in the translation. It is therefore not simply a translation but an interpretation because a 'was' is also a possible rendering.
It seems that Mark quoted Septuagint, omitting the 'am', but it is true to the Hebrew text. So, there is a possibility that Mark translated the Hebrew text himself. Moreover, the phrase "God of your father" was left out. (Would it be possible that Jesus was using an Aramaic version of the Pentateuch? The Samaritan Pentateuch, Septuagint, Acts 7:32, Justinus have "God of your fathers" instead. I have to leave this to the experts.) That's all for the text. Let's go to the theology.
God exists in eternity. There is no past, present and future for God. All creatures have a beginning and an end. There is a past, a present and a future for them. Some elementary particles come into existence for less than a millionth of a second and exist no long, no more. Not a trace of them can be found in the physical world. What about man? Man is born and dies. He has a beginning and an end. At least for the Sadducees, after his death, man was and is no more. While he is alive, any relationship he has is a present tense. After his death, the relationship is a past tense. God exists in eternity, but not man. If man is like elementary particles and exists no long no more after death, his relationship with God will also be a past tense. A relationship is made up of at least two parties. It is mutual and when one party exists no more, the relationship exists no more. It becomes history. It is a past tense. (Of course, God remains self-sufficient in the Mystery of the Blessed Trinity, without any needs of human relationships.) Following the logic of the Sadducees, since Abraham existed no more after death, God could only mean "I was the God of Abraham." when He told Moses that "I, the God of your father, the God of Abraham, the God of Isaac and the God of Jacob." (Exodus 3:6)
Septuagint adds an "am", telling us that not only does God continue to exist forever, but also man even after his death. Had man existed no more after death, Septuagint would have said "I was the God of Abraham ..." instead. I think Jesus based his argument on this grammatical point. Therefore, he concluded that "He is not God of the dead, but of the living" (Mark 12:27) Man exists beyond death and therefore, his relationship with God remains a present tense forever once it has been initiated. In the interpretation above, I keep my eyes on man, not on God; on man's relationship with God, not on God's relationship with man.
What was in the mind of Mark when he omitted the Septuagint "am"? To be sure, Jesus' debate with the Sadducees must have been conducted in either Hebrew or Aramaic. Therefore, it is likely that Mark did a free translation himself and betrayed some Hebrew traces (omission of verb to be). I said it was a free translation because the phrase 'God of your father' was also omitted. Very likely, Mark did not quote from Septuagint. Studying the Bible is great fun. The journey is like unto a detective story.

My God, I praise You because You are a God of the living. My existence after death is guaranteed. There is life unto eternity after death. I look forward to embracing death joyfully and uniting in Your Trinity mystery. I ask this, through Jesus Christ my Lord, Your Son, one God with the Holy Spirit, forever and ever. Amen.