רַב אָשֵׁי אָמַר: לְעוֹלָם לִכְלֵי חֶרֶס דָּמוּ, וּדְקָא קַשְׁיָא לָךְ לָא לִיטַּמּוּ מִגַּבָּן? — הוֹאִיל
Rav Ashi said: Actually, glass vessels are likened to earthenware vessels. And that which was difficult for you, that if so, glass vessels, like other earthenware vessels, should not become impure from contact of their outer side with a source of ritual impurity; since in glass vessels its inner side looks like its outer side. וְנִרְאֶה תּוֹכוֹ כְּבָרוֹ.
(י) וְעָשׂ֥וּ אֲר֖וֹן עֲצֵ֣י שִׁטִּ֑ים אַמָּתַ֨יִם וָחֵ֜צִי אׇרְכּ֗וֹ וְאַמָּ֤ה וָחֵ֙צִי֙ רׇחְבּ֔וֹ וְאַמָּ֥ה וָחֵ֖צִי קֹמָתֽוֹ׃ (יא) וְצִפִּיתָ֤ אֹתוֹ֙ זָהָ֣ב טָה֔וֹר מִבַּ֥יִת וּמִח֖וּץ תְּצַפֶּ֑נּוּ וְעָשִׂ֧יתָ עָלָ֛יו זֵ֥ר זָהָ֖ב סָבִֽיב׃
(10) They shall make an ark of acacia wood, two and a half cubits long, a cubit and a half wide, and a cubit and a half high. (11) Overlay it with pure gold — overlay it inside and out — and make upon it a gold molding round about.
The verse states concerning the Ark: “From within and from without you shall cover it” (Exodus 25:11). Rava said: This alludes to the idea that any Torah scholar whose inside is not like his outside, i.e., whose outward expression of righteousness is insincere, is not to be considered a Torah scholar.
It was taught: On that day that they removed Rabban Gamliel from his position, there was also a change in the general approach of the study hall as they dismissed the guard at the door and permission was granted to the students to enter. As Rabban Gamliel would proclaim and say: Any student whose inside, his thoughts and feelings, are not like his outside, i.e., his conduct and his character traits are lacking, will not enter the study hall.
On that day several benches were added to the study hall to accommodate the numerous students. Rabbi Yoḥanan said: Abba Yosef ben Dostai and the Rabbis disputed this matter. One said: Four hundred benches were added to the study hall. And one said: Seven hundred benches were added. When he saw the tremendous growth in the number of students, Rabban Gamliel was disheartened. He said: Perhaps, Heaven forbid, I prevented Israel from engaging in Torah study. They showed him in his dream white jugs filled with ashes alluding to the fact that the new students were worthless.That is not the case, but that dream was shown to him to ease his mind.
"From the inside and the outside you are to overlay it.” This verse is used by our sages (Yoma 72) to demand that Torah scholars must be able to demonstrate that they practice what they preach. They base this on the Ark which was gold on the inside as well as on the outside. Although no one actually saw the inside, it had to correspond to its exterior...The repetition in this verse means that one’s inside must match the image one creates for oneself on the outside. Our sages add further on this subject: “Why were the words of Torah compared to glass?, i.e. (Job, 28,17) “gold or glass cannot match its value?” Just as glass is transparent and allows you to see not only the outside but also the interior, so bearers of Torah must be transparent, not hiding character weakness not visible to their students or to their peers.
אָסוּר לָאָדָם לְהַנְהִיג עַצְמוֹ בְּדִבְרֵי חֲלָקוֹת וּפִתּוּי. וְלֹא יִהְיֶה אֶחָד בַּפֶּה וְאֶחָד בַּלֵּב אֶלָּא תּוֹכוֹ כְּבָרוֹ וְהָעִנְיָן שֶׁבַּלֵּב הוּא הַדָּבָר שֶׁבַּפֶּה...
וַאֲפִלּוּ מִלָּה אַחַת שֶׁל פִּתּוּי וְשֶׁל גְּנֵבַת דַּעַת אָסוּר, אֶלָּא שְׂפַת אֱמֶת וְרוּחַ נָכוֹן וְלֵב טָהוֹר מִכָּל עָמָל וְהַוּוֹת:
A person is forbidden to act in a smooth-tongued and luring manner. One should not speak one thing outwardly and think otherwise in their heart. Rather, one's inner self should be like the self which they show to the world. What one feels in their heart should be the same as the words on their lips.... It is forbidden to utter a single word of deception or fraud. Rather, one should have only truthful speech, a proper spirit and a heart pure from all deceit and trickery.
It is well known, that whoever exhibits conflicting or contradictory behavior in word or deed - people do not believe in their integrity and have no confidence in their truthfulness. Likewise, if our exterior conflicts with our interior, if our heart's intent conflicts with our words, if our physical activities are not consistent with the convictions of our soul - our service to our God will not be whole, for God will not accept from us fraudulent service, as written "I cannot [bear] iniquity with assembly" (Isaiah 1:13)...