Reference for Ketubot 118:12

ונפלגו בכתובה בעלמא ועוד תניא בש"א אינה מניקה אלא מחוורתא מתניתין דלא כב"ש:

Then let them dispute with regard to the ketubah in general. Furthermore, it was taught: Beth Shammai said: She is not obligated to nurse her child. Rather, clearly our mishnah is not in agreement with Bet Shammai.

Jastrow

Jastrow

Jastrow

Jastrow