Rashi on Exodus 12:8/רש"י על שמות י״ב:ח׳

1את הבשר AND THEY SHALL EAT] THE FLESH — but not the sinews and bones (Mekhilta).

2ומצות על מררים AND UNLEAVENED BREAD WITH מררים — Every bitter herb is called מרור. He commanded them to eat something bitter as a reminder of: (Exodus 1:14) “And they made their lives bitter” (Pesachim 116b).