Bulugh al-Maram 1420
Narrated Ibn 'Abbas (RA):
The Prophet (ﷺ) said to a man, "Do you see the sun?" He replied, "Yes." He said, "Give witness in a similar case [which is as clear as the sun], or leave it."

[Ibn 'Adi reported it with a Da'if (weak) chain or narrators, and al-Hakim graded it Sahih (authentic), but he was mistaken].
وَعَنِ ابْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا; { أَنَّ اَلنَّبِيَّ ‏- صلى الله عليه وسلم ‏-قَالَ لِرَجُلٍ: "تَرَى اَلشَّمْسَ ?" قَالَ: نَعَمْ.‏ قَالَ: "عَلَى مِثْلِهَا فَاشْهَدْ, أَوْ دَعْ" }  أَخْرَجَهُ اِبْنُ عَدِيٍّ بِإِسْنَادٍ ضَعِيفٍ, وَصَحَّحَهُ اَلْحَاكِمُ فَأَخْطَأ َ  1‏ .‏‏1 ‏- الكامل لابن عدى ( 6 / 2213 )‏ وهو على أحسن أحواله ضعيف جدا كما تقدم ( 1389 )‏.‏