Reference for Psalms 139:17

וְלִ֗י מַה־יָּקְר֣וּ רֵעֶ֣יךָ אֵ֑ל מֶ֥ה עָ֝צְמוּ רָאשֵׁיהֶֽם׃

How weighty also are Thy thoughts unto me, O God! How great is the sum of them!