Du'a for a father's protection from sickness

اللَّهُمَّ أَبْعِدْ عَنْهُ الْمَرَضَ، وَارْزُقْهُ طُولَ الْعُمْرِ فِي طَاعَتِكَ

Allahumma ab'id 'anhul-marad, warzuqhu tulal-'umri fi ta'atik

O Allah, keep sickness away from him, and grant him a long life in Your obedience.

A general supplication, not a narration from the Prophet (peace be upon him).