This is the inspired translation/commentary by Shri Brahmananda Sarasvati of one verse from a longer poem by Shankaracharya.
The verse is inspiring on many levels: it suggests that through good association-attaching your self to others who believe that awakening is possible-your awakening will be possible. When you associate with others who are focused on enlightenment, then your own progress towards that goal will be not only encouraged but also assured. You can live as a liberated soul-a jivanmukta. Yes, enlightenment is a possibility for you in this lifetime! God dwells in your heart as your own self-so let your heart sing. Bhaja means to sing and to tell the stories of God, and as you do you are able to enter into your own heart and come closer to your beloved. This adventure is only for the wise ones, not for those who are deluded and still feel their body and minds as separate from the cosmic unchanging reality-body of the Divine.
Keeping good company or satsang could be considered a practice of shaucha, one of the niyamas that Patanjali gives as a practice that could help to hasten the dawning of awakening or yoga. Shaucha means cleanliness. To keep yourself and your surroundings clean is one of the ways that one can practice shaucha. But shaucha means more than physical cleanliness. It also means cleanliness of mind. To a yogi the only real dirt is the dirt of avidya or ignorance of the true Self. When you are ignorant, you are deluded and mistake who you are for your temporary body and mind. Delusion disallows you from recognizing your divine self and so you are also unable to see the divine in others.
One of the best ways to clean the mind is to be careful about what you expose it to. The mind is like a clear crystal. A crystal will take on the color of whatever it is near-it will reflect its surrounding environment. In the same way your mind is colored by what you expose it to. If you hang out with criminals you will most likely become a criminal yourself and land in jail. But it can work in more subtle ways than that. For example, if you watch television or movies or read magazines or books which have disturbing content-e.g., violence and/or gratuitous sex-your mind and your thoughts will become tainted by those images, and your life will thereafter be negatively affected. But if you instead immerse yourself in reading inspirational books and even watching movies that inspire, educate and uplift, you will begin to purify your mind. Consciously purifying your speech will also positively affect the content of your mind. Refraining from “swear words” (words that defame God, natural bodily functions or sex), as well as from gossip and hurtful words that are used divisively, will purify your mind.
Sat means ‘truth” and anga means “attachment,” so the word satsang means “to be attached to the truth” (satsanga is the Buddhist equivalent). Traditionally satsang meant to keep the company of the enlightened, to spend time with your guru or a saint or to make pilgrimage to a holy place where a saint may have lived or taught. Of course it is not always possible to live 24/7 with a saint, so the practice of satsang involves doing your best to make the most of your time. It doesn’t mean that you immediately have to quit your job, move away from your family or divorce your husband or wife because they are not yogis. What it does mean is that when you do have a choice as to how to spend your free time, you spend it with kindred spirits. You go to a yoga class every day after work, you attend evening meditation classes or join a kirtan group and chant God’s name, or attend a weekly lecture on the Bhagavad Gita, or sign up for Sanskrit lessons, or go away for a weekend spiritual retreat. Satsang can also take more subtle forms, like surrounding yourself with inspiring books and reading the Yoga Sutra, Hatha Yoga Pradipika, biographies of saints and yogis or mystical poetry. You can also start your own satsang, by inviting people to your house to practice meditation together once a week, or form a study group around a book that has inspired you.
Above all be careful not to fall into the holier than thou trap where you use satsang to segregate yourself off from others in order to criticize or judge others as unconscious, ignorant, bad or unholy people. Remember that the purpose of satsang is to strengthen and broaden your mind so that ultimately you will be able to see clearly and perceive the divinity in all beings and be comfortable in all situations-being yourself the illuminated crystal which radiates the light of love, O wise one.