परित्राणाय साधूनां विनाशाय च दुष्कृताम्।
धर्मसंस्थापनार्थाय संभवामि युगे युगे।।4.8।।
।।4.8।। साधु पुरुषों के रक्षण दुष्कृत्य करने वालों के नाश तथा धर्म संस्थापना के लिये मैं प्रत्येक युग में प्रगट होता हूँ।।
The word sadhunam meaning virtuous refers to the sadhus or the saintly devotees, the eminent Vaisnavas who diligently seek refuge in Lord Krishna in every thing they think and do. These persons feel that without seeing and perceiving the Supreme Lord, without chanting His names, without continuously reminiscing over His phenomenal pastimes and without meditating on Him that there lives are devoid and empty and they find it difficult to even carry on their existence. There are even those with whom a single moment of absence from the Lord is like a lifetime. For the protection of these virtuous and holy beings, lest they in their agony of separation from me expire from this world, Lord Krishna bequeaths upon them the privilege of being able to perceive His confidential appearances and pastimes and partake in communion with Him. So in summary the following reasons of Lord Krishnas avatars or incarnations is: 1) for protecting the virtuous 2) for destroying the wicked 3) for re-establishing dharma or eternal righteousness which had become obscured. As dharma to all beings is factually the primary mode of worship for the Supreme Lord Krishna and His authorised avatars in order to attain moksa or salvation from the cycle of birth and death in the material existence; it should be known as the highest good for all beings. The words yuge yuge meaning from millennium to millennium is to indicate that the Supreme Lords incarnations may appear at anytime not being limited to a particular yuga.