John H. Walton summarized it best,
“Throughout the Old Testament, the burden of the text is to convince the Israelites that there was only one God…God did not confuse them with Trinitarian elaboration. As a result, it is generally contended that the Israelites did not know about the Trinity.”
Walton continually demonstrated this claim in his exegetical work and comparative studies; and it is the crux of the supposed Trinitarian implications found in Genesis 1-3. Simply put, if there was no authorial intention to mark a Trinitarian understanding of God, and if the original audience had no indication to understand such concepts, the Trinity is not an exegetical find in the text of Genesis 1-3.
Given the New Testament’s (NT) inspired testimony to the Trinity, however, Christians naturally and unhesitatingly read their theology back into the text. It is certainly not ipso facto wrong to assume that the Trinity existed and each person had a role in creation; but the point is that the Trinity is not within the passage but it is brought to the passage sensus plenior. To clarify: sensus plenior is a hermeneutic only granted to the NT authors under the inspiration of the Holy Spirit, and as such, the NT can generate meaning for an Old Testament (OT) passage beyond its original intent and audience. Truly, with the NT hermeneutic at play, all of these OT passages become neutral in regards to the Trinity. Therefore, the issued point value is based on the specific passage at hand, and attempts to determine the Trinity on the exegetical spectrum that is hermeneutically permissible for non-NT authors. Conclusively, all Trinitarian interpretations of these passages are eisegitical.
Genesis 1:1 – The fact that Elohim is a plural noun offers no sway in the discussion of the Trinity. Surely, if the original audience would have identified this plural noun for God as referring to a plurality within the godhead, then one could draw some Trinitarian intention in the original author; but given the emphatic monotheism engrained into the Israelite worldview, one will struggle to make a case that they (the original audience) understood this plural noun as indicating any modification to their strict monotheism. The several noted plural words with singular understandings in Hebrew provide an easier explanation for the plurality than assuming an OT Trinitarian understanding. In regards to Schaeffer’s comments on Genesis 1:1 (in Genesis in Space and Time), they are strictly retrospective and grounded in the NT authors’ fuller revelation in Christ. Of course, the New Testament adamantly affirms the preexistence of Jesus, but this is hardly pictured as the result of their direct engagement with Genesis 1:1. Without Trinitarian implications contained within the authorial intent and original meaning, there is no exegetical foundation for the Trinity in Genesis 1:1. There is, however, also no denial or contradiction of the Trinitarian understanding of God elucidated later through Christ.
Genesis 1:2 – Walton seemed most convincing in his exegesis of Genesis 1:2. The Israelites would not have understood ruaḥ as “a separate entity [person], but as an extension of Yahweh’s power and authority” – e.g. similar to the ‘hand of the Lord.’ Furthermore, the New Testament teaching does not explicitly contend for the Holy Spirit’s role in creation. As such, there is no authorial intent or New Testament sensus plenior to allow for an exegetical claim for the Trinity in Genesis 1:2. One’s insertion of the Holy Spirit into their interpretation of ruaḥ in Genesis 1:2 is highly eisegetical and hangs-on only by presuppositional terminological threads.
Genesis 1:26 – The ancient near eastern (ANE) context demonstrated by Walton provided a sensible and coherent understanding for the use of plurals in Genesis 1:26. Again, since Trinitarian concepts are completely foreign to the original authors and audience, a Trinitarian interpretation of the passage seems highly unlikely. Furthermore, being that the ANE was pervaded by a belief in the ‘heavenly court’ and ‘heavenly assembly,’ and since 1 Kings 22:19-22, Isaiah 14:13, and Job 1 reflect an agreement with that belief, the cultural likelihood outweighs the theological unlikelihood. The plurals most likely reflect God’s counsel with the angels, where man is created in the imago dei just as angels were created in the imago dei.
Genesis 3:15 – Contra Walton, Genesis 3:15 appears to be an intended messianic prophecy. Rydelnik asserted, “Gen. 3:15 ultimately predicts the coming of a future individual (a ‘seed’) who will have victory over the serpent through his own death.” Ancient interpretations highly favor such messianic interpretations for Gen. 3:15: “This messianic reading of Gen. 3:15 is evident in the Septuagint and the rabbinic literature of the Targumim Pseudo-Jonathan, Neofiti, Onqelos and the Midrash Genesis Rabbah 23:5.” Additionally, the earliest attestation for the messianic view is found in the early church fathers Justin (ca. 160 CE) and Irenaeus (ca. 180 CE). It is no moot point “that this text was understood by the Jewish community to point to the Messiah almost three hundred years before Jesus was born.” However, the deliverer noted in the protoevangelium shows no indication of divinity, and it stretches nowhere near asserting a Trinitarian understanding of God. It may be possible to retrospectively read the virgin birth into the feminine pronoun of Genesis 3:15; but such is the definition of eisegesis.
 John H. Walton, Genesis, New International Version Application Commentary (Grand Rapids, MI: Zondervan, 2001), 77.
 Ibid., 77.
 Michael Rydelnik, The Messianic Hope: Is the Hebrew Bible Really Messianic? (Nashville, TN.: B&H Academic, 2010), 134.
 Ibid., 137. See R. A. Martin’s analysis of the LXX in Walter C. Kaiser Jr., The Messiah in the Old Testament (Grand Rapids, Mich.: Zondervan, 1995), 40. “The LXX seems to have had a messianic understanding of the verse, for, as has been pointed out, the independent personal pronoun hu occurs more than one hundred times, but this is the only one that the LXX translates literally with autos, although the Greek idiom would require the neuter.” Victor P. Hamilton, The Book of Genesis: Chapters 1-17, New International Commentary On the Old Testament Series (Nashville, Tenn.: Wm. B. Eerdmans Publishing Company, 1990), 199.
 For an extensive list of Messianic view supporters throughout history, see Herbert W. Bateman IV, Darrell L. Bock, and Gordon H. Johnston, Jesus the Messiah: Tracing the Promises, Expectations, and Coming of Israel’s King (Grand Rapids, MI: Kregel Academic & Professional, 2011), 471.
 Kaiser, The Messiah in the Old Testament, 40.