Need help with the name of an old kung fu movie

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There is an old Kung Fu movie where a mother trained her two sons to beat an old Kung Fu Master.  The father was killed by the master.  The mother trained her two sons on her own.  I remember in particular how the mother trained one of the boys to be invincible.  She scolded his entire body in a tub of hot water and had the brother use a whip on him immediately afterwards.  Most of the movie was the two training and getting stronger.  The ended up defeating the Master in the end.  I cannot remember the name of this movie.  It was as good as The Executioners of Shaolin.

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This movies was back in the 70s.  It was one of the Saturday morning Kung Fu movies.