' To say to you [that] just as [in the case of] iron, one sharpens its fellow; so, too, two Torah scholars sharpen each other in [matters of] halacha" (Taanit 7a).
The interaction of study partners is meant to be intense, boisterous, even argumentative.
Reish Lakish agrees to the offer – as did (apparently) Rav Yochanan’s sister, though we only hear from her later – and Rav Yochanan teaches Reish Lakish Torah, making him into “a great man.” Eventually the student becomes the chavruta of the teacher, not to mention his brother-in-law and closest friend.
They learned together for years and hundreds of their disputes are recorded in the Talmud.
Perhaps there was no more powerful chavruta than that of Rav Yochanan and Reish Lakish.