If the father tells the son 'shev v'al taaseh' - do not return the article, he must not be obeyed...then why need the mishneh tell us not to obey the father in a 'kum va'aseh' go and recover the aveidoh from the beis hakevoros...this should be obvious!!!
Chaim Kahan, london england
It seems to me that this Mishnah is an example of "Lo Zu Af Zu." The Mishnah first teaches a smaller chidush ("Lo Zu"): that if the father tells the son to transgress actively (Kum va'Aseh), the son must not listen to him. Then the Mishnah teaches that not only to sin in an active way must the son not listen to the father, but "Af Zu" -- even to sin in a passive way the son may not listen to the father.
An example of "Lo Zu Af Zu" may be found later in Bava Metzia, on 38a. Rashi there (DH l'Rabanan) teaches that if the Mishnah would have said the bigger chidush at the beginning of the Mishnah, it would not have been necessary to say the other part of the Mishnah. Nevertheless, the Mishnah chose to say a smaller Chidush to start off with and then say a bigger Chidush. (One does not say that the bigger Chidush should be said first and then the smaller Chidush would be obvious, and in this way the Mishnah will be shorter. Perhaps the reason for this is that the Mishnah wishes to stress how big a Chidush the second one is, and therefore it sayss that not only can one say the first Chidush, but one can say even the bigger Chidush.)