The inclination of man's heart is evil from youth/ "for the imagination of man's heart is evil from his youth"/ sunce the devisings of man's mind are evil from his youth
Human nature is fundamentally evil, and a person's harmful impulses are evident from a young age.
("And the Lord smelled the pleasing aroma, and the Lord said in His heart: I will not again curse the ground because of man, for the inclination of man's heart is evil from his youth; nor will I again strike down every living thing as I have done" - Genesis 8:21 (the Lord after the sacrifice offered by Noah after the flood), and also: "Our Rabbis taught: The evil inclination is so strong that even its Creator called it 'evil,' as it is said: 'For the inclination of man's heart is evil from his youth'" - Kiddushin 30b)
Translation
Expression (Hebrew)
יֵצֶר לֵב הָאָדָם רַע מִנְּעֻרָיו
Definition (Hebrew)
טִבְעוֹ הַבְּסִיסִי שֶׁל הָאָדָם הוּא רַע. הַדְּחָפִים הָרָעִים שֶׁל הָאָדָם נִיכָּרִים בּוֹ כְּבָר מִגִּיל צָעִיר.
("וַיָּרַח ה' אֶת רֵיחַ הַנִּיחֹחַ וַיֹּאמֶר ה' אֶל לִבּוֹ לֹא אֹסִף לְקַלֵּל עוֹד אֶת הָאֲדָמָה בַּעֲבוּר הָאָדָם כִּי יֵצֶר לֵב הָאָדָם רַע מִנְּעֻרָיו וְלֹא אֹסִף עוֹד לְהַכּוֹת אֶת כָּל חַי כַּאֲשֶׁר עָשִׂיתִי"- בְּרֵאשִׁית ח כא (ה' לְאַחַר הַקָּרְבָּן שֶׁהִקְרִיב נֹחַ אַחֲרֵי הַמַּבּוּל ), וְכֵן:"שָׁנוּ רַבּוֹתָנוּ: קָשֶׁה יֵצֶר הָרָע שֶׁאֲפִלּוּ יוֹצְרוֹ קְרָאוֹ "רַע", שֶׁנֶּאֱמַר:"כִּי יֵצֶר לֵב הָאָדָם רַע מִנְּעֻרָיו"- קִדּוּשִׁין ל ע"ב)