(as) tough as leather
Having great strength of body, mind, or will; no susceptible to sickness or injury. My grandmother is tough as leather—she lived through the Great Depression and raised four kids pretty much all on her own! That guy's tough as leather; 400 consecutive games, and not even a sprained ankle.
tough as leather
1. If something is as tough as leather, it is very tough. Her hands were tough as leather.
2. If someone is tough as leather, they have a strong character or body and do not get upset or hurt easily. He's shown he's tough as leather.