מֵרֵאשִׁית֙ עֲרִסֹ֣תֵיכֶ֔ם תִּתְּנ֥וּ לַיהוָ֖ה תְּרוּמָ֑ה לְדֹרֹ֖תֵיכֶֽם׃ (ס)
Of the first of your dough ye shall give unto the LORD a portion for a gift throughout your generations.
Read kabbalistic (mystical) interpretation of Numbers 15:21: and classical mystical sources.