(Exodus 12:7) "And they shall take from the blood": I might think either by hand or by vessel; it is, therefore, written (Ibid. 22) "And you shall dip it in the blood which is in the saf," whereby we are apprised that he digs out a trough in the lintel and slaughters (the lamb, [the blood dripping]) into it, "saf" signifying a lintel, as in (Ezekiel 43:8) "When they placed their threshold ('sipam') next to My threshold," and (Isaiah 6:4) "And the posts of the threshold ('sippim') shook." These are the words of R. Yishmael.