From it (i.e. the previous chapter subject) [Among That Lying Will Spread Until A Man Will Testify While His Testimony Was Not Requested And A Man Will Take An Oath While His Oath Was Not Sought] Jami` at-Tirmidhi 2303
Arabic hadith text
حَدِيثِ عُمَرَ بْنِ الْخَطَّابِ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " خَيْرُ النَّاسِ قَرْنِي ثُمَّ الَّذِينَ يَلُونَهُمْ ثُمَّ الَّذِينَ يَلُونَهُمْ ثُمَّ يَفْشُو الْكَذِبُ حَتَّى يَشْهَدَ الرَّجُلُ وَلاَ يُسْتَشْهَدُ وَيَحْلِفُ الرَّجُلُ وَلاَ يُسْتَحْلَفُ " . وَمَعْنَى حَدِيثِ النَّبِيِّ صلى الله عليه وسلم " خَيْرُ الشُّهَدَاءِ الَّذِي يَأْتِي بِشَهَادَتِهِ قَبْلَ أَنْ يُسْأَلَهَا " . هُوَ عِنْدَنَا إِذَا أُشْهِدَ الرَّجُلُ عَلَى الشَّىْءِ أَنْ يُؤَدِّيَ شَهَادَتَهُ وَلاَ يَمْتَنِعَ مِنَ الشَّهَادَةِ هَكَذَا وَجْهُ الْحَدِيثِ عِنْدَ بَعْضِ أَهْلِ الْعِلْمِ
Translation
Clarification of this is in the Hadith of 'Umar bin Al-Khattab, from the Prophet(s.a.w) who said
"The best of people are my generation, then those who follow them,then those who follow them. Then lying will spread, until a man testifies while his testimony was not requested, and a man will take an oath while an oath was not sought."