Muwatta Malik, Book 36, Hadith 4 (USC-MSA)

Malik related to me that Rabia ibn Abi Abd ar-Rahman said, "An Iraqi man came before Umar ibn al-Khattab and said, 'I have come to you because of a matter which has no beginning and no end.' Umar said, 'What is it?' The man said, 'False testimony has appeared in our land.' Umar said, 'Is that so?' He said, 'Yes.' Umar said, 'By Allah! A man is not detained in Islam without just witnesses.' "

وَحَدَّثَنِي مَالِكٌ، عَنْ رَبِيعَةَ بْنِ أَبِي عَبْدِ الرَّحْمَنِ، أَنَّهُ قَالَ قَدِمَ عَلَى عُمَرَ بْنِ الْخَطَّابِ رَجُلٌ مِنْ أَهْلِ الْعِرَاقِ فَقَالَ لَقَدْ جِئْتُكَ لأَمْرٍ مَا لَهُ رَأْسٌ وَلاَ ذَنَبٌ ‏.‏ فَقَالَ عُمَرُ مَا هُوَ قَالَ شَهَادَاتُ الزُّورِ ظَهَرَتْ بِأَرْضِنَا ‏.‏ فَقَالَ عُمَرُ أَوَقَدْ كَانَ ذَلِكَ قَالَ نَعَمْ ‏.‏ فَقَالَ عُمَرُ وَاللَّهِ لاَ يُؤْسَرُ رَجُلٌ فِي الإِسْلاَمِ بِغَيْرِ الْعُدُولِ ‏.‏

sunnah.com

also referenced under: Book 36, Hadith 1405 (In-Book)

Malik related to me that Umar ibn al-Khattab said, "The testimony of some one known to bear a grudge or to be unreliable is not accepted."

وَحَدَّثَنِي مَالِكٌ، أَنَّهُ بَلَغَهُ أَنَّ عُمَرَ بْنَ الْخَطَّابِ، قَالَ لاَ تَجُوزُ شَهَادَةُ خَصْمٍ وَلاَ ظَنِينٍ ‏.‏

sunnah.com

also referenced under: Book 36, Hadith 1406 (In-Book)

Yahya said from Malik that he heard from Sulayman ibn Yasar and others that when they were asked whether the testimony of a man flogged for a hadd crime was permitted, they said, "Yes, when repentance (tawba) appears from him." Malik related to me that he heard Ibn Shihab being asked about that and he said the like of what Sulayman ibn Yasar said. Malik said, "That is what is done in our community. It is by the word of Allah, the Blessed, the Exalted, 'And those who accuse women who are muhsan, and then do not bring four witnesses, flog them with eighty lashes, and do not accept any testimony of theirs ever. They indeed are evil-doers, save those who turn in tawba after that and make amends. Allah is Forgiving, Merciful.' " (Sura 24 ayat 4).

قَالَ يَحْيَى عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ عَنْ سُلَيْمَانَ بْنِ يَسَارٍ، وَغَيْرِهِ، أَنَّهُمْ سُئِلُوا عَنْ رَجُلٍ، جُلِدَ الْحَدَّ أَتَجُوزُ شَهَادَتُهُ فَقَالُوا نَعَمْ إِذَا ظَهَرَتْ مِنْهُ التَّوْبَةُ ‏.‏

sunnah.com

also referenced under: Book 36, Hadith 1407 (In-Book)