The view of the three Imams—Mālik, al-Shāfiʿī, and Aḥmad—is that the testimony of a litigant or of anyone under suspicion is not admissible. Their evidence is the report, “The testimony of an adversary or of one suspected is not accepted,” transmitted by Abū Dāwūd in al-Marāsīl (p. 286). Ibn Ḥajar comments that the report has no sound chain, yet its various routes lend one another support.
Ibn al-Qayyim writes: “The Sacred Law has forbidden the acceptance of an enemy’s testimony against the one he opposes, lest it become a pretext for achieving his aim through false witness. The majority agree that such enmity affects legal rulings.”
Third: the qāniʿ—that is, the household servant wholly devoted to serving, running errands, and showing loyalty to the family. Because the servant’s welfare and needs are tied to the household, over which they have authority and strong influence, he is presumed to wish to avert harm from them or secure benefit for them; therefore, his testimony is ruled inadmissible.
Rawḍ al-Murbiʿ states: “The testimony of a person known for partisanship or excessive zeal is not accepted, because suspicion arises from it.”
2 – The jurists mention additional causes for rejecting testimony, among them the testimony of direct-line relatives—ascendants, no matter how far back, and descendants, no matter how far down. The testimony of any of them in favor of another is not accepted. Ibn Rushd said: “They agree unanimously that a father’s testimony for his son, a son’s for his father, and likewise a mother’s for her son and a son’s for his mother, is rejected because of the suspicion created by kinship.”
3 – According to most scholars, the testimony of one spouse in favor of the other is likewise inadmissible, for each has free access to the other’s property, so suspicion is present.
4 – By contrast, testimony from direct-line relatives against one another is accepted, as is the testimony of one spouse against the other, in view of the verse: “Stand firmly for justice, as witnesses for Allah, even against yourselves, your parents, or close relatives” (Al-Nisāʾ 4:135). Imām Aḥmad affirmed this, and al-Muwaffaq said: “I have found no dissent on the point.”