אֵ֤ל ׀ יְהוָה֮ וַיָּ֪אֶר לָ֥נוּ אִסְרוּ־חַ֥ג בַּעֲבֹתִ֑ים עַד־קַ֝רְנ֗וֹת הַמִּזְבֵּֽחַ׃
The LORD is God, and hath given us light; Order the festival procession with boughs, even unto the horns of the altar.
Read kabbalistic (mystical) interpretation of Psalms 118:27: and classical mystical sources.