Sefer HaChinukh Mitzvah 539
Can copy this into an AI, or connect the whole library to your assistant. For deeper learning, you can directly use the original seforim, sites, and apps.
שֶׁלֹּא לְהַעֲלִים עֵינָיו מִמֶּנָּה – שֶׁלֹּא נַעֲלִים עַיִן מֵאֲבֵדַת אַחֵינוּ (ב"מ כו ב), אֲבָל נִקָּחֶהָ וּנְשִׁיבָהּ אֵלָיו, וְעַל זֶה נֶאֱמַר (דברים כב ג) לֹא תוּכַל לְהִתְעַלֵּם.
To not avoid his eyes from it: That we should not avoid our eye from the lost item of our brother (Bava Metzia 26b), but we [rather] take it and return it to him. And about this is it stated (Deuteronomy 22:3), “you may not ignore [it].”
כָּל עִנְיַן הַמִּצְוָה כָּתוּב בְּמִצְוַת עֲשֵׂה שֶׁלּוֹ (מצוה תקלח) שֶׁבְּסֵדֶר זֶה.
The whole matter of this commandment is written in its [corresponding] positive commandment (Sefer HaChinukh 538) in this Order.