Light א֗וֹר “Or” of Tehillim 119 (verse 105) is wisdom from the [Torat YHVH , תוֹרַ֥ת יְהֹוָֽה] or “Law-[of] YHVH” referenced in (verse 1) :
“Your-word [is a] lamp to-my-feet, and-[a]-light for-my-path.” (נֵר־לְרַגְלִ֥י דְבָרֶ֑ךָ וְ֝א֗וֹר לִנְתִיבָתִֽי)
“Praiseworthy are those whose way is perfect, who walk with-[the]-Law of YHVH.” (אַשְׁרֵ֥י תְמִֽימֵי־דָ֑רֶךְ הַ֜הֹֽלְכִ֗ים בְּתוֹרַ֥ת יְהֹוָֽה)
For legal matters, King David was required to walk with his own copy of the Torah [Deuteronomy 17:18-19].
“And it will be, when he sits upon his royal throne, that he shall write for himself two copies of this Torah on a scroll from [that Torah which is] before the Levitic kohanim.” (יחוְהָיָ֣ה כְשִׁבְתּ֔וֹ עַ֖ל כִּסֵּ֣א מַמְלַכְתּ֑וֹ וְכָ֨תַב ל֜וֹ אֶת־מִשְׁנֵ֨ה הַתּוֹרָ֤ה הַזֹּאת֙ עַל־סֵ֔פֶר מִלִּפְנֵ֖י הַכֹּֽהֲנִ֥ים הַֽלְוִיִּֽם)
[Deuteronomy 17:19] The King is required to walk with Torah : “And it shall be with him, and he shall read it all the days of his life, so that he may learn to fear the Lord, his God, to keep all the words of this Torah and these statutes, to perform them” (וְהָֽיְתָ֣ה עִמּ֔וֹ וְקָ֥רָא ב֖וֹ כָּל־יְמֵ֣י חַיָּ֑יו לְמַ֣עַן יִלְמַ֗ד לְיִרְאָה֙ אֶת־יְהֹוָ֣ה אֱלֹהָ֔יו לִ֠שְׁמֹ֠ר אֶת־כָּל־דִּבְרֵ֞י הַתּוֹרָ֥ה הַזֹּ֛את וְאֶת־הַֽחֻקִּ֥ים הָאֵ֖לֶּה לַֽעֲשׂתָֽם)
Psalm 119 is a song about the legal light of Torah required for Kings of Israel to guide them in the decisions of their daily life.