Musnad Ahmad 177
It was narrated that Jabir bin Samurah said:
Umar addressed the people in al­-Jabiyah, and said: The Messenger of Allah ﷺ stood as I am standing and said: `Treat my Companions kindly, then those who come after them, then those who come after them. Then there will come people who will swear oaths before being asked to swear and will give testimony before being asked to 
give testimony. Whoever among you would like to attain the best place in Paradise, let him adhere to the jama'ah (the main body of Muslims), for the Shaitan is with one and he is further away from two. No man should be alone with a woman because the Shaitan will be the third one present. Whoever feels pleased when he does a good deed and feels bad when he does an evil deed is a believer.”
حَدَّثَنَا جَرِيرٌ، عَنْ عَبْدِ الْمَلِكِ بْنِ عُمَيْرٍ، عَنْ جَابِرِ بْنِ سَمُرَةَ، قَالَ خَطَبَ عُمَرُ النَّاسَ بِالْجَابِيَةِ فَقَالَ إِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَامَ فِي مِثْلِ مَقَامِي هَذَا فَقَالَ أَحْسِنُوا إِلَى أَصْحَابِي ثُمَّ الَّذِينَ يَلُونَهُمْ ثُمَّ الَّذِينَ يَلُونَهُمْ ثُمَّ يَجِيءُ قَوْمٌ يَحْلِفُ أَحَدُهُمْ عَلَى الْيَمِينِ قَبْلَ أَنْ يُسْتَحْلَفَ عَلَيْهَا وَيَشْهَدُ عَلَى الشَّهَادَةِ قَبْلَ أَنْ يُسْتَشْهَدَ فَمَنْ أَحَبَّ مِنْكُمْ أَنْ يَنَالَ بُحْبُوحَةَ الْجَنَّةِ فَلْيَلْزَمْ الْجَمَاعَةَ فَإِنَّ الشَّيْطَانَ مَعَ الْوَاحِدِ وَهُوَ مِنْ الِاثْنَيْنِ أَبْعَدُ وَلَا يَخْلُوَنَّ رَجُلٌ بِامْرَأَةٍ فَإِنَّ ثَالِثَهُمَا الشَّيْطَانُ وَمَنْ كَانَ مِنْكُمْ تَسُرُّهُ حَسَنَتُهُ وَتَسُوءُهُ سَيِّئَتُهُ فَهُوَ مُؤْمِنٌ‏.‏