Guru Nanak (1469-1539) in his epic work, Japji, explains the essential nature of God, creation, life, death and enlightenment. Yet, there is but one commandment in Japji--Jap!---MEDITATE! 
Guru Nanak teaches us that prayer, philosophy, good deeds, studying scripture and spiritual practices (including yoga) are valuable parts of a good life. However, in the end, the infinity of God can only be fully experienced through the constant repetition and remembrance of His Name.
Before creation of this world, before even time and space came into being, all that existed was the unmanifested, unimaginable and timeless ONE. Out of nothingness, God spontaneously created existence for His own play; for no other purpose than to have it realize itself and be reabsorbed into its source.
Existence started with a pure, primal, solitary vibration. Everything that has ever been or ever will be is but a permutation, a further ripple emanating from that first pebble tossed on the seamless and infinite original pond of peace. As humans, we are created as spiritual beings. That is, we have the in-born capacity to realize our own essential nature; to authentically experience the source of life and the beginning of time.
To make the drama of self-realization even more entertaining, God "blessed" mankind with the five senses of sight, hearing, smell, taste and touch. These doors of perception provide us with "pleasure." The mind is then tricked into thinking that everlasting happiness can be attained by satisfying  the demands of  these senses. We are then put in the position of trying to find happiness outside of ourselves. In focusing all of our attention on the outside world, we have become strangers to our own soul, our own inner voice. This is what we would call self-alienation and spiritual emptiness.
Guru Nanak and the all the other great spiritual masters have given us an antidote for this existential emptiness. And that is the practice of meditation. By disciplining our minds to repeat God's Name, we become increasingly aware of the infinite reality that can only be found within. Whether we chant Wahe Guru, Jehovah, Allah, Krishna...it's all the same. God has manifested himself into the material world in infinite ways; so He has infinite Names.
In time, The Name becomes so absorbed into the fabric of our being, that we and The Name become ONE. This ultimately brings us to the moment of creation, when all that existed was God's Name. In that very moment, God-awareness, self-realization, spiritual ecstasy is experienced. Meditation has many wonderful benefits, stress reduction and mental clarity to name just two. But ultimately we meditate to experience our soul and become One with the Creator.