I wanted to briefly mention the gospels contain allegorical narratives that convey profound spiritual meanings. Two obvious examples are the resurrection and the casting out of demons or evils spirits. Clearly, from a Baha'i perspective, do they invalidate the Bible or make it less authentic? Some would argue yes, others no. I'm clearly in the "No" camp. The resurrection is an essential aspect of Christianity, Islam and the Baha'i Faith. We need to look no further the what Baha'u'llah has said in the Kitab-i-Iqan. In Islam it tied in with ends times eschatology.
Angels, demons and Satan are all part of Islam and even the Baha'i writings. Baha'i take demons and Satan metaphorically and so do many Christians. Many don't of course and take it literally along with the resurrection narrative. OTOH I don't see how God could have taught about these concepts had they not been woven into the story about the life and Teachings of Jesus. Our role as Baha'is is to demonstrate using the Bible itself and persuasive argument, the true significance of these concepts. That is exactly what Abdu'l-Baha did. He never denigrated the bible or said anything negative about it. To the contrary;
"The Bible and the Gospels are most honored in the estimation of all Baha'is. One of the spiritual utterances of His Holiness Christ in his Sermon on the Mount is preferable to me to all the writings of the philosophers. It is the religious duty of every Baha'i to read and comprehend the meanings of the Old and New Testament."
(Abdu'l-Baha, Star of the West, Vol. 14, p. 55)
THIS book is the Holy Book of God, of celestial Inspiration. It is the Bible of Salvation, the Noble Gospel. It is the mystery of the Kingdom and its light. It is the Divine Bounty, the sign of the guidance of God.
Bahá'í Reference Library - ‘Abdu’l-Bahá in London, Pages 17-18
"...all the Prophets of Israel were centers of inspiration; Christ also was a receiver of inspiration, but what a difference between the inspiration of the Word of God and the revelations of Isaiah, Jeremiah and Elijah!"
'Abdu'l-Bahá,
Some Answered Questions
Furthermore, it is significant and convincing that when Muhammad proclaimed His work and mission, His first objection to His own followers was, “Why have you not believed on Jesus Christ? Why have you not accepted the Gospel? Why have you not believed in Moses? Why have you not followed the precepts of the Old Testament? Why have you not understood the prophets of Israel? Why have you not believed in the disciples of Christ? The first duty incumbent upon ye, O Arabians, is to accept and believe in these. You must consider Moses as a Prophet. You must accept Jesus Christ as the Word of God.
You must know the Old and the New Testaments as the Word of God. You must believe in Jesus Christ as the product of the Holy Spirit.”
Bahá'í Reference Library - The Promulgation of Universal Peace, Pages 197-203
I found a couple more passages from the Universal House of Justice that are relevant to our discussion.
In studying the Bible Bahá'ís must bear two principles in mind. The first is that many passages in Sacred Scriptures are intended to be taken metaphorically, not literally, and some of the paradoxes and apparent contradictions which appear are intended to indicate this. The second is the fact that the text of the early Scriptures, such as the Bible, is not wholly authentic.
(28 May 1984 to an individual believer)
The Bahá'ís believe what is in the Bible to be true in substance. This does not mean that every word recorded in that Book is to be taken literally and treated as the authentic saying of a Prophet. A striking example is given in the account of the sacrifice which Abraham was called upon to make. The Guardian of the Faith confirms that the record in the Qur'an and the Writings of Bahá'u'lláh, namely that it was Ishmael, and not Isaac as stated in the Old Testament, whom Abraham was to sacrifice, is to be upheld. In one of His Tablets 'Abdu'l-Bahá refers to this discrepancy, and explains that, from a spiritual point of view, it is irrelevant which son was involved. The essential part of the story is that Abraham was willing to obey God's command to sacrifice His son. Thus, although the account in the Torah is inaccurate in detail, it is true in substance....
...The Bahá'ís believe that God's Revelation is under His care and protection and that the essence, or essential elements, of what His Manifestations intended to convey has been recorded and preserved in Their Holy Books. However, as the sayings of the ancient Prophets were written down some time later, we cannot categorically state, as we do in the case of the Writings of Bahá'u'lláh, that the words and phrases attributed to Them are Their exact words
(9 August 1984 to an individual believer)
I agree.