סימן קד סעיף ב
עוֹד אָמְרוּ רַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה, הַמְבַזֶּה אֶת חֹל הַמּוֹעֵד, אַף עַל פִּי שֶׁיֵּשׁ בְּיָדוֹ תּוֹרָה וּמַעֲשִׂים טוֹבִים, אֵין לוֹ חֵלֶק לָעוֹלָם הַבָּא. וְהַמְבַזֶּה, הַיְנוּ, שֶׁאֵינוֹ מְכַבְּדוֹ בְּמַאֲכָל וּבְמִשְׁתֶּה וּבִכְסוּת. וְלָכֵן כָּל אָדָם חַיָּב לְכַבְּדוֹ כְּפִי כֹּחוֹ, וְלִלְבוֹשׁ בְּגָדִים מְכֻבָּדִים (אבות פרק ג. וּבְחַיֵּי אָדָם, וְסִימָן תק"ל).
In addition, our Rabbis, of blessed memory, said:6Pirkei Avos 3:11. "He who disgraces Chol Hamoed, even though he has to his credit Torah and good deeds, has no share in the World to Come." Disgracing Chol Hamoed implies not honoring it with better food and wearing better clothes.7Rashi and Bartenura (Pirkei Avos). Rabbeinu Yonah and Sha’ar Hakedushah explain that it means not desecrating Chol Hamoed by doing a melachah. Therefore, every man is obligated to honor it according to his means,8See Sha’ar Hatziyun 530:4. You are obligated to honor it, but not to the extent that you are obligated on Yom Tov. Therefore, although it is meritorious to eat two meals a day with bread, it is not an actual obligation. Also your clothing should be nicer than during the weekdays, but need not be Shabbos clothing. (see Magein Avraham 664:3) In our times, many people including Chassidim and Bnei Torah, wear their Shabbos clothing on Chol Hamoed, especially in Eretz Yisroel. This was also the custom of the Maharil. and to wear dignified clothing.
תנא דבי אליהו כל השונה הלכות בכל יום מובטח לו שהוא בן העולם הבא שנאמר הליכות עולם לו אל תקרי הליכות אלא הלכות (נדה ע"ג.)