Better a little with righteousness than a large income with injustice.
אמר רבא בשעה שמכניסין אדם לדין אומרים לו נשאת ונתת באמונה
Rava said: After departing from this world, when a person is brought to judgment for the life he lived in this world, they say to him: Did you conduct business faithfully?
והישר בעיניו תעשה זה משא ומתן מלמד שכל מי שנושא ונותן באמונה ורוח הבריות נוחה הימנו מעלין עליו כאלו קיים את כל התורה כולה.
This refers to integrity in one's business dealings with others. We are hereby taught that if one deals in business faithfully with others, such that society takes pleasure in dealing with him, it is awarded to him as if he fulfilled the entire Torah.
You shall not commit a corruption in judgement; in dry measure, in weight, or in liquid measure. Exact scales and exact weights, an exact dry measure and an exact liquid measure you shall have for yourselves, I am Adonoy, your God who has taken you out of the land of Egypt.
(יג) לֹֽא־יִהְיֶ֥ה לְךָ֛ בְּכִֽיסְךָ֖ אֶ֣בֶן וָאָ֑בֶן גְּדוֹלָ֖ה וּקְטַנָּֽה׃ (ס) (יד) לֹא־יִהְיֶ֥ה לְךָ֛ בְּבֵיתְךָ֖ אֵיפָ֣ה וְאֵיפָ֑ה גְּדוֹלָ֖ה וּקְטַנָּֽה׃ (טו) אֶ֣בֶן שְׁלֵמָ֤ה וָצֶ֙דֶק֙ יִֽהְיֶה־לָּ֔ךְ אֵיפָ֧ה שְׁלֵמָ֛ה וָצֶ֖דֶק יִֽהְיֶה־לָּ֑ךְ לְמַ֙עַן֙ יַאֲרִ֣יכוּ יָמֶ֔יךָ עַ֚ל הָֽאֲדָמָ֔ה אֲשֶׁר־ה' אֱלֹקֶ֖יךָ נֹתֵ֥ן לָֽךְ׃ (טז) כִּ֧י תוֹעֲבַ֛ת ה' אֱלֹקֶ֖יךָ כָּל־עֹ֣שֵׂה אֵ֑לֶּה כֹּ֖ל עֹ֥שֵׂה עָֽוֶל׃ (פ)
(13) You shall not have in your bag different weights, a large and a small. (14) You shall not have in your house different measures, a large and a small. (15) A perfect and just weight shall you have; a perfect and just measure shall you have; that your days may be long upon the land which the Lord your God gives you. (16) For everyone who does such things, everyone who does wrong is an abomination to the Lord your God.
דא"ר לוי קשה עונשין של מדות יותר מעונשין של עריות
As Rabbi Levi said: The harshness of the punishment for using dishonest measures is more than the punishment for transgressing the prohibition of forbidden relationships
If you lend money to My people, to the poor among you, do not act toward them as a creditor; you should exact no interest from them. If you take your neighbor's clothing as a collateral, you must return it to him before the sun sets; it is his only clothing, the sole covering for his skin. In what else shall he sleep? Therefore, if he cries out to Me, I will pay heed, for I am compassionate.