Read and reflect on verse 777 from Surah Al-Maaida: Thus it will be more likely that people will offer testimony in accordance with the truth-or else they will [have cause to] fear that their oaths will...
ذَٰلِكَ أَدْنَىٰ أَنْ يَأْتُوا بِالشَّهَادَةِ عَلَىٰ وَجْهِهَا أَوْ يَخَافُوا أَنْ تُرَدَّ أَيْمَانٌ بَعْدَ أَيْمَانِهِمْ ۗ وَاتَّقُوا اللَّهَ وَاسْمَعُوا ۗ وَاللَّهُ لَا يَهْدِي الْقَوْمَ الْفَاسِقِينَ
Thus it will be more likely that people will offer testimony in accordance with the truth-or else they will [have cause to] fear that their oaths will be refuted by the oaths of others. Be, then, conscious of God, and hearken [unto Him]: for God does not bestow His guidance upon iniquitous folk.