Milton Plate 1,(E 95) "Bring me my Bow of burning gold: Bring me my Arrows of desire: Bring me my Spear: O clouds unfold! Bring me my Chariot of fire! I will not cease from Mental Fight, Nor shall my Sword sleep in my hand: Till we have built Jerusalem, In Englands green & pleasant Land."
Focusing on 'my Chariot of fire' we can have a look at Blake's use of the term in another context.
Vision of the Last Judgment, (E 560) "If the Spectator could Enter into these Images in his Imagination approaching them on the Fiery Chariot of his Contemplative Thought if he could Enter into Noahs Rainbow or into his bosom or could make a Friend & Companion of one of these Images of wonder which always intreats him to leave mortal things as he must know then would he arise from his Grave then would he meet the Lord in the Air & then he would be happy General Knowledge is Remote Knowledge it is in Particulars that Wisdom consists & Happiness too. Both in Art & in Life General Masses are as Much Art as a Pasteboard Man is Human Every Man has Eyes Nose & Mouth this Every Idiot knows but he who enters into & discriminates most minutely the Manners & Intentions [P 83] the [Expression] Characters in all their branches is the alone Wise or Sensible Man & on this discrimination All Art is founded. I intreat then that the Spectator will attend to the Hands & Feet to the Lineaments of the Countenances they are all descriptive of Character & not a line is drawn without intention & that most discriminate & particularBlake has derived his image of the chariot of fire from the character of Elijah in the Old Testament. Blake considers Elijah to be the prophet who best represents the prophetic character. The prophets acted as intermediaries between God and man. Through their intuitive visionary connection, the word of God was perceived through contemplation. The imagination of Blake was inspired by the account in the book of Second Kings of Elijah ascending to heaven in the whirlwind riding his chariot of fire.
much less an Insignificant Blur or Mark> ... By the side of Seth is Elijah he comprehends all the Prophetic Characters he is seen on his fiery Chariot bowing before the throne of the Saviour."
2nd Kings 2
 Fifty men of the sons of the prophets also went, and stood at some distance from them, as they both were standing by the Jordan.
 Then Eli'jah took his mantle, and rolled it up, and struck the water, and the water was parted to the one side and to the other, till the two of them could go over on dry ground.
 When they had crossed, Eli'jah said to Eli'sha, "Ask what I shall do for you, before I am taken from you." And Eli'sha said, "I pray you, let me inherit a double share of your spirit."
 And he said, "You have asked a hard thing; yet, if you see me as I am being taken from you, it shall be so for you; but if you do not see me, it shall not be so."
 And as they still went on and talked, behold, a chariot of fire and horses of fire separated the two of them. And Eli'jah went up by a whirlwind into heaven.
 And Eli'sha saw it and he cried, "My father, my father! the chariots of Israel and its horsemen!" And he saw him no more.Then he took hold of his own clothes and rent them in two pieces.
 And he took up the mantle of Eli'jah that had fallen from him, and went back and stood on the bank of the Jordan.
 Then he took the mantle of Eli'jah that had fallen from him, and struck the water, saying, "Where is the LORD, the God of Eli'jah?" And when he had struck the water, the water was parted to the one side and to the other; and Eli'sha went over.
|Image from the Blake Society|
Milton, Plate 1, (E 96)
"Would to God that all the Lords people were Prophets. Numbers XI. ch 29 v."
 But Moses said to him, "Are you jealous for my sake? Would that all the LORD's people were prophets, that the LORD would put his spirit upon them!"
 And after six days Jesus took with him Peter and James and John his brother, and led them up a high mountain apart.
 And he was transfigured before them, and his face shone like the sun, and his garments became white as light.
 And behold, there appeared to them Moses and Eli'jah, talking with him.
 And Peter said to Jesus, "Lord, it is well that we are here; if you wish, I will make three booths here, one for you and one for Moses and one for Eli'jah."
 He was still speaking, when lo, a bright cloud overshadowed them, and a voice from the cloud said, "This is my beloved Son, with whom I am well pleased; listen to him."
 When the disciples heard this, they fell on their faces, and were filled with awe.
Blake's appeal to the Lord was 'Bring me my Chariot of fire!'