Hello Rabbi! Would you recommend any mefarshim or shiurim online that describe the best arguments of why Mimachorat HaShabbat refers to first day of Pesach. I know the Ibn Ezra goes on and even brings an argument from Joshua the Karaite, which he refutes. But I don’t really understand what was going on there, as it was a little all over the place. May you please also provide a quick rundown of Ibn Ezra’s points?

In this particular case, I suggest letting the Tanach explain itself, where in Yehoshua 5, 11, it says explicitly that the new grains were eaten on the day following Pesach, not "Saturday".