Rabbi Baruch Bodenheim: Gemara Shabbos: Perek Kirah, יום חמישי, Cheshvan 22, Daf 42b Sugya – Kli Rishon/Sheini (11/13/25)
Tosfos (תוס’ דף מב: “אבל) presented a machlokes between the Rashbam and the Ri/Rabbeinu Tam whether liquids being poured from a Kli Rishon have a status of Kli Rishon or Kli Sheini – עירוי כלי ראשון ככלי ראשון או ככלי שני.
Review the משנה דף לט and learn תוס’ דף לט “כל in regards to what is permitted to pour hot liquids from a Kli Rishon and what is permitted to be placed inside a Kli Shieni.
The Rishonim discuss this machlokes at length and bring different proofs
See ר”ן & רא”ש (they are lengthy – see it quickly to get an overview)
https://hebrewbooks.org/pdfpager.aspx?req=37953&st=&pgnum=589
https://hebrewbooks.org/pdfpager.aspx?req=37953&st=&pgnum=355
Learn אגלי טל מלאכה אופה ס”ק ל”א אות א who lists the three opinions brought in Tosfos and an additional fourth opinion (Rabbeinu Yonah). See how he explains each one answers the proofs against them.
https://hebrewbooks.org/pdfpager.aspx?req=14401&st=&pgnum=255
https://hebrewbooks.org/pdfpager.aspx?req=14401&st=&pgnum=256
