chandamsi yasya parnani yastam veda sa vedavit
The Blessed Lord said
He who knows the Pipala tree which is said to be imperishable, as having its root above and branches below, and whose leaves are the Vedas, is the knower of the Vedas. 1
Urdhvamulamadhahsakltam:- [Like the first two verses of the thirteenth chapter, here in the first verse of the fifteenth chapter also the Lord presents a view of all the topics of the entire chapter. The expression 'Urdhvamulam' denotes God; the expression 'Adhahsakham denotes Brahma, the representative of all beings while the term 'Aivattham' denotes the world. He who knows the omnipotent Lord (the root of the Pipala tree in form of the universe) in reality has been called 'Vedavit' (knower of the Vedas).
Generally trees have their roots below and branches above. But this tree in the form of the universe is strange as it has its root above and branches below. The supreme abode of God from where there is no return is above all the other worlds. Brahma is the main branch (stem) of the tree in the form of the world as he emanates first of all. The ahode of Brahma is lower than that of God. Brahma is lower than God in position, virtues, rank and age etc., so he is called 'Adhah'. As the root is the foundation (support) of the entire tree, so is God the origin of the entire universe. Brahma, the creator is horn of Him and he has been described by the expression 'Adhahsakham' (branches below).
God is the illuminator and base of the entire creation and He is superior to everyone in evcryway. "There is none equal to Thee, how could then there be one superior to Thee in the three worlds" (Gita 1l/43)? Being the base and the support of the entire universe He is called 'Urdhvamalam' (root above).
The term 'Mula' stands for the root or the base. The universe is born of Him and is preserved by Him. He is eternal, infinite and the base of the entire creation. He resides in His eternal abode, which is situated above all the worlds in His manifested form with attributes. So He is known as 'Urdhva'. This world is born of Him and therefore it is called 'Urdhvamala' having its root above.
As trunks, branches and tendrils sprout from the root of the tree, so does the entire umverse emanate from God. It is expanded by Him, it remains established in Him and it is by His power that beings act. Having taken refuge in such Lord, a person is satisfied forever (the Lord talks of taking refuge in Him in the fourth verse).