Mishkat al-Masabih 1181
Marthad b. ‘Abdallah said:
I went to ‘Uqba al-Juhani and said, “I can tell you something about Abu Tamim which will make you wonder. He prays two rak'as before the sunset prayer.” ‘Uqba replied, “We used to do so in the time of God’s Messenger.” I asked, “What prevents you now?” and he replied, “Work.” 

Bukhari transmitted it.
وَعَن مرْثَد بْنِ عَبْدِ اللَّهِ قَالَ: أَتَيْتُ عُقْبَةَ الْجُهَنِيَّ فَقُلْتُ: أَلَا أُعَجِّبُكَ مِنْ أَبِي تَمِيمٍ يَرْكَعُ رَكْعَتَيْنِ قَبْلَ صَلَاةِ الْمَغْرِبِ؟ فَقَالَ عُقْبَةُ: إِنَّا كُنَّا نَفْعَلُهُ عَلَى عَهْدِ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ. قُلْتُ: فَمَا يَمْنَعُكَ الْآنَ؟ قَالَ: الشّغل. رَوَاهُ البُخَارِيّ