Ibn Rajab al-Hanbali:
“And whoever is mindful of Allah (and keeps to His boundaries) in his youth during his years of strength, then Allah will preserve him in his old age when his strength weakens. And He will allow him to enjoy and benefit from his sense of hearing, sight, capabilities, strength and mind/intellect.
One particular scholar had passed the age of 100 and still continued to benefit from his strength of body and mind. One day, he took a great leap and jumped up high, and the people rebuked him for that. So he said: “We preserved these limbs of ours from sin when we were younger, so Allah has preserved them for us in our old age.”
– Jami’ ‘Ulum wal-Hikam
سبيل الرشاد 