Midrash for Pesachim 4:1
מְקוֹם שֶׁנָּהֲגוּ לַעֲשׂוֹת מְלָאכָה בְּעַרְבֵי פְסָחִים עַד חֲצוֹת, עוֹשִׂין. מְקוֹם שֶׁנָּהֲגוּ שֶׁלֹּא לַעֲשׂוֹת, אֵין עוֹשִׂין. הַהוֹלֵךְ מִמְּקוֹם שֶׁעוֹשִׂין לִמְקוֹם שֶׁאֵין עוֹשִׂין, אוֹ מִמְּקוֹם שֶׁאֵין עוֹשִׂין לִמְקוֹם שֶׁעוֹשִׂין, נוֹתְנִין עָלָיו חֻמְרֵי מָקוֹם שֶׁיָּצָא מִשָּׁם וְחֻמְרֵי מָקוֹם שֶׁהָלַךְ לְשָׁם. וְאַל יְשַׁנֶּה אָדָם, מִפְּנֵי הַמַּחֲלֹקֶת:
In a place where it was the custom to work on Pesach eve until mid-day, they (are permitted to) work. In a place where it was the custom not to work, [so that they not be preoccupied with work and forget to burn the chametz, to slaughter the Pesach offering, and to prepare the matzah of mitzvah], they do not work. If one goes from a place where they work to one where they do not work, or from a place where they do not work to one where they do work, there are imposed upon him the stringencies of the place whence he came and the place to which he went. And one should not deviate because of contention. [This is what is meant: If one goes from a place where they do not work to a place where they work, there are imposed upon him the stringencies of the place whence he came, and he should not work. For we rule "Let one not deviate from the custom of the city" only because of contention. But here there is no contention! For what will those who see him not working say? "He holds that work is forbidden and disagrees with all of us"? They will not say this, but rather: "He is out of work." For "there are plenty of idlers in the marketplace" every day of the year. And "there are imposed the stringencies of the place whence he came" applies only when he intends to return there; but if not, he deports himself as the people of the place to which he went, whether for lenity or stringency.]