This is a musical performance by Saakin, of the most famous "naat" of the great Sufi Saint, Pir Mehr Ali Shah (d. 1937) - Aj Sik Mitraan di. A "naat" is a devotional poem that is sung and expresses love for the Prophet Muhammad. "Naats" are perhaps the most widespread of the "musical" traditions of the Indian Subcontinent.
This is from the original soundtrack of the film Zindagi Tamasha.