Detections of massive galaxies in the first billion years of the universe have been increasingly confirmed in recent years. This raises a question how these massive sources can be formed at such an early epoch of the universe. ALMA has been playing a central role in finding these interesting galaxies at z > 6.5, but the number has been limited. An on-going ALMA Large Program, REBELS (Reionization Era Bright Emission Line Search) has been systematically searching for ISM emission lines at z > 6.5 in 40 UV-selected massive galaxies to create a statistical sample. This large sample allows us to characterize gas, dust, and stellar mass growth in the early universe. In this talk, I will present some first results from the REBELS program.