If you want the version specifically from the movie (which includes the beautiful instrumental intro), YouTube Music is your best bet.
Here’s a draft review for a repack/remastered version of “Sun Sathiya Mahiya Barsa De” (assuming you mean the romantic track often associated with or a similar fusion track). I’ve written it as a listener review:
If you are looking for the , this guide explores the magic behind the track and how to enjoy it legally and in high quality. The Magic Behind Sun Saathiya
You can find the official "Sun Saathiya" song on platforms like Gaana and JioSaavn, where you can stream it for free (with ads) or download it for offline listening as part of a premium subscription.
You can find the official MP3 and high-quality audio links through these verified platforms: