The question asks for an idiom via the idiom-requests tag and your suggestion is hardly idiomatic, and indeed introduces "tenuously" which is not in the original at all Please be sure to answer the question
"God, tell us the reason, why youth is wasted on the young" Clearly implies the young do not know the value of what they have until much later in life And it causes them to yearn for the time which was wasted

ألا ليت الشباب يعود يومآ فأخبره بما فعل ____ من 6 حروف

May not be as descriptive a prose as you expected.

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شرح مائة المعاني والبيان
Provide details and share your research! May not be as descriptive a prose as you expected
شرح مائة المعاني والبيان
Asking for help, clarification, or responding to other answers
ألا ليت الشباب يعود يومآ فأخبره بما فعل ____ من 6 حروف
There's a similarity in the way it is pronounced and written
Provide details and share your research! "God, tell us the reason, why youth is wasted on the young" Clearly implies the young do not know the value of what they have until much later in life A certain song comes to my mind
' I just want to note that it's so eloquent in Arabic and so colourful because youthness is Shabab meaning the youth and grayness is Masheeb Any idiom, proverb or piece of poetry suchlike? There's a similarity in the way it is pronounced and written

ألا ليت الشباب يعود يومآ فأخبره بما فعل ____ من 6 حروف

Maybe as english speakers, you can't see it but in Arabic it's extremely colourful.

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قاموس معاجم: معنى و شرح ليت الشباب يعود يوما فأخبره بما فعل المشيب في معجم عربي عربي أو قاموس عربي عربي وأفضل قواميس اللغة العربية
Making statements based on opinion; back them up with references or personal experience
قاموس معاجم: معنى و شرح ليت الشباب يعود يوما فأخبره بما فعل المشيب في معجم عربي عربي أو قاموس عربي عربي وأفضل قواميس اللغة العربية
A certain song comes to my mind
شرح مائة المعاني والبيان
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