There seems to be an understanding that Aggadic Passages are not normative within Halacha.
That may be true - yet it may also be an oversimplification.
A. Darach R Simlai ...613 mitzvot
Halachot G'dolot did not take this as a normative passage and proceeded to list 613 mitzvot of all shapes and sizes
However, Rambam took this obvious Drasha and assumed it was predicated upon 14 separate axiomatic conditions!
B Standing for Qiddush Levanah.
Based upon DRASH, we greet the Shechinah whilst reciting Birkat Levana. Yet, Abbaye rules that we must stand.
C. Glass is Smooth.
The issue of glass absorbing "treif" is discussed in Avot de R. Nattan [ADRN] yet the Rashba issues his permissive ruling using an aggadic source text.
D Women wearing Tallit.
Many Posqim object to women wearing a Tallit because it violates "lo tilbash kli gever". The source text used is Targum Yonatan ben Uziel [TYBU]- a midrashic work.
However, this is a "perfect mis-understanding". Of how this is used. TYBU is not producing binding p'saq as a precdent - rather Posqim are using his text to determine if Lo tilbash applies to Talit. And they accept his Meisi'ach lefi tummo as normative that Tallit is indeed a man's garment. NOTE: this norm could be subject to change over time and place.
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