رُوِيَ عَنْ عَلِيِّ بْنِ غُرَابٍ عَنْ أَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ قَالَ: "لاَ تَشْهَدَنَّ عَلَى شَهَادَةٍ حَتَّى تَعْرِفَهَا كَمَا تَعْرِفُ كَفَّكَ".
It is narrated from Ali ibn Ghurab, from Abu Abdillah (a.s): Imam (a.s) said: "Do not testify to a testimony until you know it as clearly as you know your own palm."