אָמַ֣ר שֹׁמֵ֔ר אָתָ֥ה בֹ֖קֶר וְגַם־לָ֑יְלָה אִם־תִּבְעָי֥וּן בְּעָ֖יוּ שֻׁ֥בוּ אֵתָֽיוּ׃ (ס)
The watchman said: ‘The morning cometh, and also the night— If ye will inquire, inquire ye; return, come.’
Read kabbalistic (mystical) interpretation of Isaiah 21:12: and classical mystical sources.