רֵאשִׁית֙ עֲרִסֹ֣תֵכֶ֔ם חַלָּ֖ה תָּרִ֣ימוּ תְרוּמָ֑ה כִּתְרוּמַ֣ת גֹּ֔רֶן כֵּ֖ן תָּרִ֥ימוּ אֹתָֽהּ׃
Of the first of your dough ye shall set apart a cake for a gift; as that which is set apart of the threshing-floor, so shall ye set it apart.
Read kabbalistic (mystical) interpretation of Numbers 15:20: and classical mystical sources.