Storms may overtake you while there may be none to prick you (for reforms). Shall I be witness to my becoming heretic after acceptance of Faith and fighting in the company of the Prophet?! 
"In that case I shall be misguided and I shall not be on the right path." (Qur'an, 6:56). 
So you should return to your evil places, and get back on the traces of your heels. Beware! Certainly you will meet, after me, overwhelming disgrace and sharp sword and tradition that will be adopted by the oppressors as a norm towards you.1 
As-Sayyid ar-Radi says: In the words "wala baqiyah minkum abirun" used by Amir al-mu'minin the "abir" has been related with "ba'" and "ra'" and it has been taken from the Arab saying "rajulun abirun" which means the man who prunes the date-palm trees and improves them. In one version the word is "athir" and its meaning is "relator of good news." 
In my view this is more appropriate, as though Amir al-mu'minin intends to say that there should remain none to carry news. In one version the word appears as "abiz" with "za'" which means one who leaps. One who dies is also called "abiz".
(1) Al-Tabari, Ta'rikh, VI, 48, 3378;
(2) Ibn Qutaybah, al-'Imamah, I, 124;
(3) Sibt ibn al-Jawzi, Tadhkirah, 100;
(4) al-Tabari, al-Mustarshid, 162;
(5) Ibn al-'Athir, al-Nihayah, under (a.b.r);
(6) al-Baladhuri, Ansab, II, 369;
(7) al-Mubarrad, al-Kamil, II, 141.