Siman- Berachos Daf 3

• Rabbi Eliezer identifies the end time for Krias Shema as the end of the first mishmar (watch), to teach us that there are three heavenly watches in the evening when Hashem roars like a lion, lamenting that the sins of His children caused the destruction of the Beis HaMikdash and their exile.
• Three reasons one may not enter a churvah (ruin):

a)suspicion of inappropriate behavior

b)the danger of collapse

c)the danger of harmful mazikin found there

• The northern wind would blow across Dovid Hamelech’s harp exactly at midnight, upon which he would wake up and sing Hashem’s praises for the rest of the night.