It is narrated from Ibn Shihab: Humayd bin Abd al-Rahman bin Awf informed me that Umar bin al-Khattab and Uthman bin Affan (may Allah be pleased with them both) would both offer the Maghrib prayer when they saw the blackness of the night, that is, before breaking their fast, and then they would break their fast after the prayer.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2106