Ramp

Rashi (27:5) says that we know that the mizbaoch had a ramp from the end of Yisro that there is a negative commandment not to use steps to go up on the mizbaoch.  The Briskor Rav asks the need for a ramp is learnt in Zevachim 62a (Rashi ד"ה שכל מקום) from a different source?  And how do we see from Yisro that there must be a ramp built for the mizbaoch, all we know is that there is a violation of going up on stairs?  He explains that the issur is said לא תעלה במעלות על מזבחי, there must be a דין מזבח, it must be considered מזבחי on the part of the מזבח that the person is scaling to violate the commandment.  Ergo, there must be a כבש that has a דין מזבח on it, otherwise there would not be any violation of going up on the מזבח.  The issur teaches us that there must be a pathway up the מזבח that is considered part of the מזבח.