What is the meaning of "Keep light and overtake" in Ali ibn Abi Talib's sermon?

The following sermon from Ali ibn Abi Talib can be found in Nahj-ul-Balagha as well as in Tarikh al-Tabari. > **فإِنَّ الغَايَةَ أَمَامَكُمْ، وَإِنَّ وَرَاءَكُمُ السَّاعَةَ تَحْدُوكُمْ تَخَفَّفُوا تَلْحَقوا، فَإنَّمَا يُنْتَظَرُ بِأوَّلِكُمْ آخِرُكُمْ .** > > > Your aim (reward or punishment) is before you. Behind your back is the > hour (of resurrection) which is driving you on. Keep (yourself) light > and overtake (the forward ones). Your last ones are being awaited by > the first ones (who have preceded). [Sermon 21] It is said that Ali's saying "Keep light and overtake" in this sermon is the shortest expression with the deepest meaning. As I understand the first part of it - "keep light" - obviously refering to reduce attachment to material world and restrain from accumulating items/wealth, I am not sure about the second part -"overtake"- and the last sentence of the sermon. Answer with references would be much appreciated.