It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) used to recite "Qul ya ayyuha al-kafirun" and "Qul huwa Allahu ahad" in the Maghrib prayer.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 13338