Parashas Shemos
לֵ֣ךְ וְאָֽסַפְתָּ֞ אֶת־זִקְנֵ֣י יִשְׂרָאֵ֗ל וְאָמַרְתָּ֤ אֲלֵהֶם֙ יְהֹוָ֞ה אֱלֹהֵ֤י אֲבֹֽתֵיכֶם֙ נִרְאָ֣ה אֵלַ֔י אֱלֹהֵ֧י אַבְרָהָ֛ם יִצְחָ֥ק וְיַעֲקֹ֖ב לֵאמֹ֑ר פָּקֹ֤ד פָּקַ֙דְתִּי֙ אֶתְכֶ֔ם וְאֶת־הֶעָשׂ֥וּי לָכֶ֖ם בְּמִצְרָֽיִם׃
“Go and assemble the elders of Israel and say to them: The ETERNAL, the God of your fathers—the God of Abraham, Isaac, and Jacob—has appeared tokappeared to Or “communicated with.” me and said, ‘I have taken note of you and of what is being done to you in Egypt,
Torah Temimah points to TT (verified).
את זקני ישראל — מכאן שהקב״ה חלק כבוד לזקנים.
English: “The elders of Israel” — from here [we learn] that the Holy One accorded honor to the elders.
Custom
Chazal derive from the command that God Himself models honor toward the elders.