Musar sobre Isaías 26:9

This is likewise as the prophet said: "to Your Name and to Your remembrance is the lust of [our] soul" (Isaiah 26:8), and "my soul yearns for You in the night; my spirit within me seeks You" (Isaiah 26:9). And David himself said: "when I remember You on my bed, through the night watches I meditate about You" (Tehilim 63:7). Thus he described the pleasure and delight he experienced when speaking of and praising G-d, blessed be His Name. Likewise he said: "I will delight myself in Your Commandments, which I love" (Tehilim 119:47), and "Your testimonies are my delight..." (Tehilim 119:24).

See what is stated in the Zohar in Parashas Lech Lecha (83a) regarding the verse, “With my soul I desired You at night, even with my spirit within me I sought you out” (Yeshayahu 26:9). Rabbi Shimon ben Yochai explains that when a person climbs into bed and his soul departs, it is to the soul’s benefit if it is pure and free of blemish and iniquity and if all his ways are holy. For then his soul merits witnessing the pleasantness of Hashem and reflecting in His Temple.