The Tzlach asks: Makas bechoros was precisely at chatzos. How can Rabbi Elozar ben Azarya, who derives the time restriction of the korban pesach from makas bechoros learn that one must eat the korban until chatzos? Perhaps it should be eaten precisely at chatzos?

He answers that the time of chatzos has no continuance to it; half the night has passed and half remains, but there is no definite time called chatzos. Accordingly, it is impossible to say that one should eat the korban precisely at chatzos. Furthermore, even if there was such a time and it could be defined, it would be practically impossible to eat a k'zayis from the korban in that brief instant. It is evident that the z'man of chatzos is the end-time for the korban.

We will discuss the Radvaz tomorrow iy"H.