Know that Cain is the level of the left arm of every partzuf in every world, whether in Arich Anpin, Abba and Imma, or Zeir Anpin and Nukvah in Atzilut , or in BY"A [Beriya-Yetzira-Asiya]. Abel is just the opposite, the level of the right arm of every partzuf in every world.

The three lower worlds of BY"A are called ‘arms’, whereas the world of Atzilut is called ‘wings’. Thus, Cain is the left wing of Atzilut and Abel is the right wing of Atzilut. These levels of wings and arms have both ohr makif and ohr penimi as well.

Thought flies, Atzilut linkage provides wings.

Arms are vessels of action and doing. So are the lower worlds B"YA vessels through the designs of Atzilut, the world of thought, to act out. Thought flies, Atzilut linkage provides wings.

Atzilut is the realm of all Divinity. Connection there propels the soul to boundless levels - represented by flying. The lower realms do not ascend in the aspect of wings and connection there is only as arms.

All the souls that come from the second level that Cain and Abel inherited from their father Adam only merit to reach in this world the wings of malchut of Atzilut, called the nefesh of Atzilut - the first time. Higher than this they cannot reach the first time, only after they come back another time.

Since those from this level can reach the nefesh of Atzilut the first time, these righteous people are called ‘angels’. Any time you find the term angel used for a righteous individual they will be from this root.

"‘Bless God, ye his angels...’ (Ps. 103:19) - these are tzadikim." (Zohar) All tzadikim are angelic. Still, amongst them themselves, some are more in this category.1

Atzilut linkage lifts the soul above normal human parameters and grants it angelic status. Such individuals have aerial abilities. This manifests as super-human alacrity, especially in understanding. Also, they are able to circumvent and as if ‘fly above’ complications and get things done.

Phinehas did not need to be hidden since he was an angel...

Therefore, it says regarding Phinehas in the matter of Rahab the innkeeper2, "The woman took the two men and hid him", (Joshua 2:4) that is, in the singular. For she only had to hide one person - Phinehas did not need to be hidden since he was an angel3 and he was called that because he was from the root of Cain. Therefore Elijah is called ‘angel’4, because he is from the root of Cain.5

The wording implies that being angelic has particularly to do with the Cain root. Even though there are corresponding levels to found in the Abel root? This demonstrates the principle that Cain, the first born, has extra good. Therefore, the likelihood of a soul reaching this plateau tends to come from this source.