Q. If Baha'u'llah is the return of the Spirit (RUH) of Jesus, Who is the return of the Soul (NAFS) of Jesus?

Answer: The Soul of Jesus was the WORD of God. The WORD is ____NOT____ a Name/Attribute of ALLAH. Rather, it is His "command". ALLAH said "Be!" and created the Cosmos. God created the Cosmos through His "WORD". The WORD is not an ordinary human soul, and thus can "return" to this material world.

Baha'u'llah wrote:

"The WORD which the Son concealed is made manifest. It hath been sent down in the form of a human temple in this day." (The Proclamation of Baha'u'llah, p.83)
Most Baha'is believe He was referring to Himself as "the WORD". But I believe (as Personal Belief) that He was referring to His Son 'Abdu'l-Baha in this Verse. The Father referred to His Beloved Son Abbas as:
"A WORD which God hath adorned with the ornament of His Own Self, and made It Sovereign over the earth and all there is therein." (The World Order of Baha'u'llah, p.135)
Assadu'lllah, the secretary of 'Abdu'l-Baha, wrote:
"He is the Son of God, the only Door, the Lord of Mankind." (Sacred Mysteries, p.74)
I believe that the WORD "returns" in every Dispensation in a "cloud" (i.e. "veil"--new body and new name). Many early Baha'is believed that 'Abdu'l-Baha was the reincarnation of Jesus (i.e. the "return" of His Soul/Individuality). 'Abdu'l-Baha was not a Prophet, but a Chosen One with a "unique station" between God and Mankind.