Sri Radhikopanishad from Rigveda
Once Sages Sanaka and others who are shining with Divine power have praised Brahma Deva and enquired "Oh! God! Among all Gods and Goddesses who are prominent? What are their powers? Among these powers which is the Supreme and Primordial that has caused the existence of creation?
Responding to their questions God Brahma replied "Dear sons listen carefully. This is most sacred truth and the great secret indeed. This should be revealed only to affable Jeeva Brahmavadi and Guru Bhaktha (Devotees of Guru). If this secret is revealed to a non-devotee it would be lead to a great sin.
Lord Sri Krishna is the Supreme Lord. He is the Absolute Divine resplendent with Shadaiswarya (Six Opulences). He is incessantly served and worshipped by Go, Gopa and Gopikas (Cows, Cowherd boys and girls). He is the Lord of Vrindavan. He is the only Sarveswar. Vrinda Devi worships Him. Sriman Narayana is but His own Swaroopa. He is the Lord of all the fourteen universes and is beyond Prakrithi. He is eternal Being. He has great powers like Ahladini, Sandhini, Gnanecha and Kriya. Among them Ahladini is the most prominent power. This Shakthi is of Sri Radha. Lord Sri Krishna himself is engrossed in Her worship.
Sri Radha too worships Krishna continuously as Radhika. Sri Radhika is also known as Gandharva. Out of Her transcendental form all the wives of Krishna and Goddess Lakshmi Devi emerged.
The ocean of Rasa for the sake of Divine play has manifested as two. Sarweswari Radha equals Krishna in all the 'Kalas' (Divine aspects). She is the life of Krishna. She is the quintessential Prema Swaroopini. All the Four Vedas worship Sri Radhaji in solitude. The Rishis endowed with Brahma Gnana(Knowledge of Brahman) acclaims Her greatness. Even if I endeavour throughout my life span, I cannot fully describe Her Mahima (paramountcy)) and Her Divine play. That Jeeva who receives Grace of Sriji, he only could reach Her Divine Abode (Parama Dham). That being is a great stupid who worships only Krishna ignoring Sri Radhaji.