משנה אויף שמות 9:16

[If he says,] “A korban should be what I do not eat of yours”; “By a korban! If I eat of yours”; “What I do not eat of yours should not be a korban to me” the vow is not binding. [If he says], “An oath [that] I will not eat of yours”; “An oath that I eat of yours”; “No oath [that] I will not eat of yours” his oath is valid. In these instances oaths are more stringent than vows. There is [also] greater stringency in vows than in oaths. How so? If one says, “Konam be the sukkah that I make,”; “The lulav that I take”; “The tefillin that I put on”; as vows they are binding, but as oaths they are not, because one cannot swear to transgress the commandments.