I assume you are refering to Touchstone's bizarre comemnts to Rosalind during his conversation with her and Celia in this scene. When he is questioned by Rosalind and asked where it was that he learned the "oath" that he has expressed, he replies:
Of a certain knight that swore by his honour they were good pancakes, and swore by his honour the mustard was naught. Now I'll stand to it: the pancakes were naught and the mustard was good, and yet was not the knight forsworn.
This is typical frippery and foolishness from Touchstone that nevertheless reveals his intelligence and ability to play with words as Touchstone's "oath" leads to a succession of jokes and puns on honour and foreswearing. Pancakes were a traditional dish for Shrove Tuesday, a time of chaotic festivities to prepare for the Lenten fast. Touchstone says he learnt the oath from a knight who swore that the pancakes he was eating were good but the mustard on top of them was bad. Touchstone says it was the opposite, pointing out the humour of concepts such as honour and forswearing.