And now regarding thy question, 'How is it that no records are to be found concerning the Prophets that have preceded Adam, the Father of Mankind, or of any reference to them is no proof that they did not actually exist. That no records concerning them are now available, should be attributed to their extreme remoteness, as well as to the vast changes which the earth hath undergone since their time.

Bahá’u’lláh, Lights of Guidance, p. 500

Man, therefore, on the plane of the contingent beings is the most perfect being. By man is meant the perfect individual, who is like unto a mirror in which the Divine perfections are manifested and reflected. But the sun does not condescend from the height of its sanctity to enter into the mirror, but when the latter is purified and turned towards the Sun of Truth, the perfections of this Sun, consisting of light and heat, are reflected and manifested in that mirror. These souls are the Divine Manifestations of God.

‘Abdu’l-Bahá, Star of the West, Vol. X, p. 151

Thou hast written regarding Buddha and Confucius. Buddha was an illustrious personage. Confucius became the cause of civilization, advancement and prosperity for the people of China. Now it is not the time when we discuss concerning the stations and positions of those who are passed away. We must concentrate our attention upon the present. What hath transpired in a former time is past. Now is the time when we restrict our discussion to the Most Great Luminary of Peace and Salvation in this Age, to talk of the Blessed Perfection [Bahá’u’lláh] and to voice His exhortations, behests and teachings. Buddha and Confucius were kings in bygone ages who have disappeared. Their sovereignty in this world is ended and their cycle is completed. Now the Throne of the Kingdom of ABHA is established and the Blessed Perfection is sitting upon the Throne of Grandeur. We must raise this Call, promulgate the Word of God and live in accord with the teachings and advices of the Beauty of ABHA.

‘Abdu’l-Bahá, Tablets of ‘Abdu’l-Bahá Abbas", vol. 2, p. 469-70

Abraham and Krishna are two separate individuals, with no connection that we know of.

Shoghi Effendi, Lights of Guidance, p. 503

As our teachings do not state Zoroaster is the connecting link between the Euphrates and the Prophets in India we cannot assert this.

Shoghi Effendi, The Compilation of Compilations vol. I, p. 22

As to the religion of the Sabeans very little is known about the origins of this religion, though we Bahá’ís are certain of one thing that the founder of it has been a Divinely-sent Messenger. The country where Sabeanism became widespread and flourished was Chaldea, and Abraham is considered as having been a follower of that Faith.

Shoghi Effendi, Lights of Guidance, p. 502