This is a very significant quote that compels Muslims to do justice and tell the truth even against a loved one.

4:135 (Y. Ali) O ye who believe! stand out firmly for justice, as witnesses to Allah, even as against yourselves, or your parents, or your kin, and whether it be (against) rich or poor: for Allah can best protect both. Follow not the lusts (of your hearts), lest ye swerve, and if ye distort (justice) or decline to do justice, verily Allah is well- acquainted with all that ye do.