God is the One Who created you from a state of weakness from a ‘base fluid’ cf. Q. 328 then He ordained after a second weakness which is the weakness of the period of childhood strength that is the strength of youth then after strength He appointed weakness again and grey hair the weakness of old age and the grey hairs of decrepitude read vocalised as du‘f ‘weakness’ in all three places. He creates what He will of weakness and strength youth and grey hairs and He is the Knower of how to manage His creatures the Omnipotent.