According to Abd Allah bin Hars’s (may Allah be pleased with him) relation, the Noble Prophet (peace and blessings be upon him) stated as follows:

The sleep of the fasting person is worship, and his silence is deemed as glorifying.  many times more merits are given for his good deeds and worship. His prayers are accepted; his sins are forgiven and eliminated. (Kanz al-Ummal, 3:327)