The witness of a person falsely accusing somebody of illegal sexual intercourse and the witness of a thief or an adulterer

The Statement of Allah عز وجل: "... And reject their testimony forever, they indeed are the Fasiqun (liars, rebellious, disobedient to Allah). Except those who repent thereafter and do righteous deeds..." (V.24:4,5) Umar gave legal punishment of scourging to Abu Bakra, Shibl bin Ma'bad and Nafi' for accusing Al-Mughira for illegal sexual intercourse falsely, and then they were made to repent and he said that whoever repented, his witness would be accepted (in the future). Abdullah bin 'Utba, 'Umar bin 'Abdul Aziz, Sa'id bin Jubair, Tawus, Mujahid, Ash-Sha'bi, 'Ikrima, Az-Zuhri, Muharib bin Dithar, Shuraih and Mu'awiya bin Qurra considered it permissible (i.e., the witness of the false accusers after being punished). Abu Az-Zinad said, "Our verdict in Al-Madina is that, if the false accuser (of others of illegal sexual intercourse) withdraws the accusation and repents, then his (future) witness is acceptable." Ash-Sha'bi and Qatada said, "If he tells that he has told a lie, the punishment will be instituted against him, but his (future) witness will be accepted." Ath-Thauri said, "If a slave is scourged (for falsely accusing others of illegal sexual intercourse) and later on he is manumitted, then his (future) witness is to be accepted. If somebody who has received such punishment is made a judge, his decisions will be valid." Some people said, "The witness of a false-accuser is not to be accepted even if he repented." They added: "The marriage is not legal unless it is witnessed by two witnesses; it is permissible that the two witnesses can be those who have received such punishments, but the slaves are not to be accepted as witnesses to marriage." He accepts the witness of the person who has received the punishment (for falsely accusing others of illegal sexual intercourse) and the witness of a male slave and a female slave concerning the appearance of the new moon (i.e., crescent) (of the month of fasting etc.). How to know the repentance of a person who has received the punishment of false accusation and no doubt, the Prophet (ﷺ) ﷺ kept an adulterer in exile for a year. The Prophet (ﷺ) ﷺ did not allow anybody to talk to Ka'b bin Malik and his two companions for fifty days.