Can't remember name of this Kung Fu movie

I remember 3 young men were taught by a old monk 3 different strengths or techniques. One of the young men had to put his hands in a big bowl of hot sand everyday and he became super strong. One other student had to work the fields. That's all I can remember about this movie. I consider it one of the best Kung Fu I ever saw. Please if you can help me find the name of this classic. Thanks