And the Almighty said in Surah al-Aʿrāf:

{Call upon your Lord in humility and in secret.} (Al-Aʿrāf: 55)"

And the Almighty said in Surah Maryam:

{Kāf, Hā, Yā, ʿAyn, Ṣād. [This is] a mention of the mercy of your Lord to His servant Zechariah. When he called to his Lord a secret call (nidāʾan khafiyyan).} (Maryam: 1-3).

And the Almighty said in Surah Āl ʿImrān:

{He said, "Your sign is that you will not speak to people for three days except by symbol (ramzan)."} (Āl ʿImrān: 41). And He said in Surah Maryam, referring to the nights: {He said, "Your sign is that you will not speak to people for three nights, [being] sound [in health]."} (Maryam: 10).

What also indicates this meaning is what was mentioned in the first chapter of Jonah (Yūnān), saying: "So Jonah was in the belly of the fish for three days and three nights." This is a proof that regarding these three days and three nights, it is obligatory to hide their meaning from the Opposites (al-Aḍḍād), just as Jonah manifested his concealment during these days and nights, and Allah knows best.

And the Almighty said:

{And do not be loud in your prayer or [too] silent in it.} (Al-Isrāʾ: 110).