As-Salaam alaykum,
Sheikh Sahl Ibn Abdullah al-Tustari, may Allah be Merciful to him said that it was narrated on the authority of Ibn Mas'ud, may Allah be pleased with him that he [ibn Mas'ud] said:

"The one who knows the Qur'an by heart should be known for his
vigil at night while people are asleep; for his fasting during the day
while people are eating; for his sorrow while people are rejoicing; for
his weeping while people are laughing; and for his silence when
people are talking."

Thus who knows the Qur'an by heart should be tearful, sorrowful, wise and learned, not hard-hearted and deceptive, that is to say, not dishonest.

For more on this, see:
Sahl Abdullah al-Tustari.