260. Maariv and Ne'ilah

Tefillah u’Birkas Kohanim 1:6

Ezra and his court also instituted a nighttime prayer service since the limbs of the afternoon sacrifice could be burned all night long as per Leviticus 6:2, “The burnt offering will remain on the altar all night until morning.” Psalms 55:18 also addresses this, saying “In the evening, morning and afternoon, I will speak and call aloud, and He will hear my voice.” The evening prayer (maariv) is not obligatory the way that the morning (shacharis) and afternoon prayers are. Nevertheless, the Jewish people have universally accepted the maariv service as obligatory.

Tefillah u’Birkas Kohanim 1:7

They likewise instituted a prayer to be recited after mincha, near sunset on fast days. The reason for this service is to increase our supplication before God because of the fast. This service is called ne’ilah; the name suggests that the gates of Heaven are closing behind the sun, since it is only recited near sunset.