It is narrated from Sayyiduna Abu Ayyub al-Ansari or Sayyiduna Zayd bin Thabit (may Allah be pleased with them both), the narrator being in doubt, that the Prophet (peace and blessings be upon him) recited Surah al-A'raf in both rak'ahs of the Maghrib prayer.
Hadith Referenceالمعجم الكبير للطبراني / باب الزاي / 4806