Baha'u'llah is the Fire of Being kindled by the snow of faith, whereas the Spirit is the eyewash of light upon the prism of the heart.
Notice how Baha'u'llah's Fire of Being is lit in the conscious mind and not the subconscious mind like the Spirit is. The conscious mind is a mind without concern for past or future. It knows no rank and holds no station. It has no depth or height. It has no design and holds no symbol. It knows no support. It is a mark of crimson. It holds no eloquent speaker, except the inspiration of the heart, and Baha'u'llah Himself. It knows no plan except 'Abdu'l-Baha's Divine Plan, it has no mortal guide except Shoghi Effendi's letters. It carries out the devotion shown to it. Devotion here is one thing done at a time, and cannot be sustained except with great desire. There is no room for impressing someone. It hath no wisdom save what is stored in the heart. It sees the world as a child, 100% hope. Its energy is the ignorance of purity. Its captain is the invoker of His Word. It is stoked at the fire of responsibility. It is drowned by the remembrance of aught except Him.