It is narrated from Sayyiduna Salamah bin Akwa’ (may Allah be pleased with him) that I used to travel with the Prophet (peace and blessings of Allah be upon him), and I never saw him offering voluntary prayers after the ‘Asr or Fajr prayers.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16535