Nevertheless as the Torah spoke in human terms in order that a person can understand to the human capacity, as such, it was given permission to the Kabbalistic teachers to speak about the Sefiros and to use examples in order for us to understand them, and therefore they called it lights.
The reason for this is as it helps us understand a little bit how God connects to His emotions / Sefiros, for it is similar to the unity of the light of the Sun within the actual Sun itself.
Now the Sun is called the source of light and the ray of light that emanates from it is called light.
This is as the verse says, “And God called to light, day.”
Now when the light is within its source, within the sun itself, then it is so unified with it, for there only the sun itself shines, as within the Sun, the light and the Sun are a single entity, and it has no separate existence whatsoever.
Now literally this reality but much much is the same comparison to the emotions of God, and His desire and His intelligence and God Himself.
In the world of Atzilus God-Himself goes into them and connects to them completely.
But in actual fact, this Unity is far greater and deeper than the unity of The Light within the Sun, as God’s ways are much greater than ours.
Nevertheless in order to make it understood, therefore there is an example of the light of the Sun within the Sun as there it is one – and completely subsumed within its source – in fact, it has no separate identity whatsoever, only the identity of the source itself.
Similarly the emotions of God and His desire and His wisdom are not actually real, they are only real as they exist relative to the Creations / Beings within heaven and Earth.
In other words, as their creation, life-force and master plan that God gives them with His will and wisdom and knowledge and comprehension as they go into His emotions, as the Medrash states that, “With 10 things this world was created wisdom, knowledge, comprehension etc.” and as Elijah the Prophet said, that “You created 10 “Garments,” you called them 10 Sefiros with which you direct hidden unrevealed Worlds, and revealed worlds and through this you conceal yourself.
For example on the first day of the six days of creation the attribute / emotion of Chessed, as it includes all the other Holy emotions and His desire and His wisdom and His knowledge and His comprehension created the light in the saying “Let there be light.”
Now this concept is the expansion and the drawing of the light to this world from above, and it’s expansion in the world to spread from one end to the other, which is the nature of Chessed / kindness, unconditional giving.
It is only because Chessed also has the attribute of Gevurah strength therefore it was not as spiritual as the light in heaven, and furthermore could come into this world which is a limited spatial dimension.
In a similar Sense, on the second day, the attribute of Gevurah / strength as it is combined with the other attributes and God’s will etc. was created, and with it He created the sky, as it said, “Let there be a sky separating the waters” – which is the level of concealment and strength to conceal the higher Waters which are spiritual from the lower Waters and thereby the lower Waters became physical and they separated from the higher Waters.
Now though this is a Gevurah, the level of Chessed is combined – as it states, “The world was built through Chessed” which includes every aspect of it.
The reason this separation was a kindness is for the entire purpose of the sky is so that the dry land can exist and then man has a location where he can serve God.
This is what Elijah said in Tikkunim, “So we can grasp how the world is managed both through Justice and compassion…. though this occurs not to an understandable Justice, for God’s justice and Essence is compassion – and in fact God transcends all these emotions entirely.”