Know in one's heart
To understand and know something without giving it outward expression.
(Modern Hebrew)
Translation
Expression (Hebrew)
יָדַע בְּלִבּוֹ
Definition (Hebrew)
הֵבִין וְיָדַע מִבְּלִי לָתֵת לְכָךְ בִּיטּוּי חֲצוּנִי
(הָעִבְרִית הַחֲדָשָׁה)