[Acacia Tree at night in south Israel; a reminder of the letter "shin" in Hebrew, the first letter of HaShem's Holy Name Sh-add-ai]

[The Night Says:]

To relate Your lovingkindness in the morning,

and Your faithfulness in the nights.
(Tehillim 92:3)

Night symbolizes faith in G-d.  The darkness of night symbolizes exile and travail, times when we  cannot see the fulfillment of G-d's promises but our faith remains.   Our ancestors, for believing in G-d, they were found worthy of having the Divine Presence rest upon them and they chanted songs.  Our ancestors experienced this joyousness in reward for having stayed faithful to G-d in this world that resembles total night.

[MeAm Lo'ez, Perek Shira]