Musnad Ahmad 1060:37

Isma'il narrated to us, Muhammad ibn Ishaq informed us, from Yazid ibn Abi Habib, from Marthad ibn 'Abdullah al-Yazani, who said: Abu Ayyub came to us as a warrior, and 'Uqbah ibn 'Amir was in charge of Egypt at that time. He delayed the Maghrib prayer. Abu Ayyub stood up to him and said: "What is this prayer, O 'Uqbah?" He replied: "We were occupied." He said: "As for me, by Allah, it is only that I fear people will think you saw the Messenger of Allah (peace and blessings of Allah be upon him) doing this. Have you not heard the Messenger of Allah (peace and blessings of Allah be upon him) say: 'My nation will continue to be in goodness, or upon the natural disposition (fitrah), as long as they do not delay the Maghrib prayer until the stars become intertwined'?"