The Third Section of Chapter One of the Sefer Yetzirah is about perception and also, acceptance. The author is warning against over-intellectualizing. The sheer Celestial Beauty of what is being described is amazing.
The appearance of the Ten Sefiroth out of Nothingness is as a flash of lightning or a sparkling flame, and they are without beginning or end. The Word of God is in them when they go forth and when they return. They run by Divine Order like a whirlwind and humble themselves before the Holy Throne. The Sefiroth out of Nothingness have their end linked to their beginning and their beginning linked to their end, just as the flame is wedded to a live coal; because the Lord is One and there is not a second one, and before one what will you count? Concerning the fact that there are Ten Sefiroth out of Nothingness; shut your mouth from speaking and your heart from thinking. If your mouth rushes to speak and your heart rushes to think, return, for thus it is said: "And the Living Creatures ran and returned," and upon this Mystery a Covenant was made.
Much has been made of the “lightning flash”. The Ten Sefiroth are found in the Universe as well as the human body. This resembles the concept of “Kundalini” (“coiled energy”) in Tantra and Yoga. The description here of the Energy of God running up and down through the Ten Sefiroth is referring to this same energy. First, it is said, that there is neither begging nor end of the Ten Sefiroth. This Energy passes up and down the spinal column through the Sushumna Nadi. This is a reflection of the Divine One, Whose Singular Presence permeates all things. The writer also urges us not to think too deeply about the Quantity of Sefiroth. This reminds one of Chapter Fifty-Six of the Tao Te Ching. The quote towards the end is from Ezekiel. The mentions in the Sefer Yetsirah of God's Throne have sparked volumes. This is known as the Merkabah ("throne") literature, based on Ezekiel's visions.
And the living beings would run and return, like the appearance of the sparks.
Ezekiel was speaking of a Class of Angels.