When the sun declines toward the west at noontime...

When the sun declines toward the west at noontime, it is the time for al-Dhuhr Salah (prayer), except for the optional Salah (prayer) before it, which is up to you to make it longer or shorter.’” Sa‘id has narrated from Musa al-Hassan from al-Hassan ibn al-Husayn al-Lu’lu’i from Safwan ibn Yahya from al-Harith ibn al-Mughirah al-Nadriy and ‘Umar ibn Hanzalah: In a similar Hadith it is said, ‘It is up to you to make the optional one light thereafter, or make it longer, thereafter is the time (for al-Dhuhr).”’

صحيح - Allamah Baqir al-Majlisi (Mirʾāt al-ʿUqūl fī Sharḥ Akhbār Āl al-Rasūl (15/33))