אכן יש ה’ במקום הזה ואנכי לא ידעתי (ויצא כח: טז)

Yaakov said that he did not know that one can serve Hashem through sleeping ‘לשם שמים’ – for the sake of Heaven.  Until now, Yaakov learned in the Yeshiva of Shem and Ever, and he thought that only by learning the Torah could he serve Hashem.  But now, when he realized that יש ה’ במקום הזה – also through sleep can one serve Hashem – as one is busy regaining one’s strength to continue serving Him with a rested body and a rejuvenated spirit.