In the morning Hashem will make known the one who is His own etc.

When I remember You upon my couch, in night watches I meditate upon You.

A person who rests at night on his bed like a Yid, and he remembers Hashem Yisborach, so too will his awakening in the morning will be as a Yid needs to awaken. And so will be his actions all day like it is befitting for a true Yid. It is hinted in the words “Boker viyodah Hashem ess asher lo - In the morning Hashem will make known the one who is His own". Implying, from a person's level in the morning we can know how his heart was with Hashem when he laid on his bed at night.

• Sefer Divrei Shmuel - Slonim