The distinguished scholar Zayd bin Muhammad bin Haadi al Madkhali (rahimahullah) mentions:
...[What] is intended here by [the word] " 'adaalah" (integrity) is- one of the four conditions which are obligatory to fulfill in [relation] to a narrator of hadeeth. The four conditions of the narrator: The first [is] Islaam, thus it [a narration of hadeeth] is not accepted from the disbeliever.
The second [is] takleef (stage of accountability) at the time of the narration, and what is meant by this is [to have reached] puberty and [to have sound] intellect.
The third [is] dhabt (precision), and it's meaning is [for the narrator] to relay what he is carrying in the manner of which it was relayed to him without [any] addition or subtraction.
The fourth, from the conditions of accepting a narration, is 'adaalah (integrity). And what is intended by 'adl linguistically is the opposite of Jūr (unjust/corrupt). And the technical [religious meaning, of 'adl], the scholars define with multiple definitions concurrent in meaning even if they differ in wording. I will limit the definitions to two.
- The definition of Ibn al-Lahaam al-Hanbali- He said: "It is preservation of religion, firmness upon sticking to taqwa (piety) and murooa'h (manhood), without innovation accompanying it, to actualize staying away from major sins, avoiding persistence upon lesser sins and some of the permissible [things]." (1)
- The definition of Ibn Hajar-He said: "[An] attribute [that] fortifies [one] upon adhering to taqwa, a sense of honor; and what is intended by taqwa [is]: to steer clear of evil deeds, from shirk (polytheism), or Fisq (immorality), or innovation. (2)
As [one] recognizes integrity by two things:
The first of them [is]: istiqaamah (uprightness) and shuhrah (reputation), like one who his integrity was well known amongst the scholars during his time, or [the] time of those after him. Like the four Imaams, the possessors [meaning authors] of the Sihaah (plural of Saheeh), the Sunan and other than them.
The second of them [is]: tansees (quotation) [of statements about a person's integrity] from those who their statements are accepted, from the scholars of Jarh wa T'adeel (Criticism and Praise).
As for jahaalah (ignorance) linguistically [is the] opposite of knowledge; as [being] uneducated is contradictory [to being] learned. And it['s religious meaning], with the scholars of the science of hadeeth is: absence of familiarity [with] a narrator or being devoid of awareness of specific praise of him or criticism of him, and it has it's reasons with the scholars of expertise of the technical [science].
This speech is in relation to that which is connected to [the] condition [of] the narrator, and similar to it [in regards to that] which is connected to the witness and news. ...(3)
1. al-Mukhtasir pg. 84
2. Nuzhat-ul-Nathar pg. 55
3. Source: al-Ajwibat-ul-Athariyah an al-masaai'l-il-minhajeeyah...First addition Pgs. 9 & 10