Al-Allaamah Siddeeq Hasan Khan (rahimahullaah) said:

Indeed, the one who combines five characteristics will be acquainted with the truth and the greatest of them is (1) Sincerity, (2) (sound) understanding and (3) justice.  (4)Fourthly-the scarcest to be found and (people) are mostly deprived of it–is eagerness in acquainting (oneself) with the truth and being keen in calling to it.


[Source: Qatf Ath-Thamar Fee Bayaani Aqeedati Ahlil Athar: page 175]