That which is upon his heart
Figuratively: what he feels. His emotions or thoughts (originally: what is placed upon the chest).
("And he told her all his heart, and said to her, A razor has not come upon my head, for I am a Nazirite to God from my mother's womb" – Judges 16:17, and also: "And thus you will learn that the High Priest, in the garments of the ephod, and the breastplate was surrounded before and behind by the names of the twelve tribes, the breastplate that is upon his heart, in front of it were set the names of the twelve tribes" – Rabbeinu Bahya, Exodus, chapter 28)
Translation
Expression (Hebrew)
אֲשֶׁר עַל לִבּוֹ
Definition (Hebrew)
בְּהַשְׁאָלָה: אֶת הַדְּבָרִים שֶׁהוּא חָשׁ. אֶת רִגְשׁוֹתָיו אוֹ מַחְשְׁבוֹתָיו (בַּמָּקוֹר: מָה שֶׁמֻּנָּח עַל הֶחָזֶה).
("וַיַּגֶּד לָהּ אֶת כָּל לִבּוֹ וַיֹּאמֶר לָהּ מוֹרָה לֹא עָלָה עַל רֹאשִׁי כִּי נְזִיר אֱלֹהִים אֲנִי מִבֶּטֶן אִמִּי"- שׁוֹפְטִים טז יז, וְכֵן:"וְנִמְצֵאתָ לָמֵד שֶׁהַכֹּהֵן הַגָּדוֹל בְּבִגְדֵי הָאֵפוֹד וְהַחֹשֶׁן הָיָה מֻקָּף מִלְּפָנָיו וּמֵאַחֲרָיו מִשְּׁמוֹת י"ב שְׁבָטִים, הַחֹשֶׁן אֲשֶׁר עַל לִבּוֹ מִלְּפָנָיו הָיוּ קְבוּעִים שְׁמוֹת י"ב הַשְּׁבָטִים"- רַבֵּנוּ בְּחַיַּי שְׁמוֹת פֶּרֶק כח)