Sahih Muslim Book - 5, Hadith - 1448

وَحَدَّثَنِى أَبُو بَكْرِ بْنُ نَافِعٍ الْعَبْدِىُّ حَدَّثَنَا بَهْزُ بْنُ أَسَدٍ الْعَمِّىُّ حَدَّثَنَا حَمَّادُ بْنُ سَلَمَةَ عَنْ ثَابِتٍ. أَنَّهُمْ سَأَلُوا أَنَسًا عَنْ خَاتَمِ رَسُولِ اللَّهِ -صلى الله عليه وسلم- فَقَالَ أَخَّرَ رَسُولُ اللَّهِ -صلى الله عليه وسلم- الْعِشَاءَ ذَاتَ لَيْلَةٍ إِلَى شَطْرِ اللَّيْلِ أَوْ كَادَ يَذْهَبُ شَطْرُ اللَّيْلِ ثُمَّ جَاءَ فَقَالَ « إِنَّ النَّاسَ قَدْ صَلَّوْا وَنَامُوا وَإِنَّكُمْ لَمْ تَزَالُوا فِى صَلاَةٍ مَا انْتَظَرْتُمُ الصَّلاَةَ ». قَالَ أَنَسٌ كَأَنِّى أَنْظُرُ إِلَى وَبِيصِ خَاتَمِهِ مِنْ فِضَّةٍ وَرَفَعَ إِصْبَعَهُ الْيُسْرَى بِالْخِنْصَرِ.

It was narrated from Thabit that they asked Anas about the ring of the Messenger of Allah (s.a.w) and he said: "One night the Messenger of Allah (s.a.w) delayed 'Isha' until the middle of the night, or when almost half of the night had gone. Then he came and said: 'The people have prayed and gone to sleep, but you are still in a state of prayer so long as you are waiting for the prayer.' Anas said: 'It is as if I can see the brightness of his silver ring, and he raised the little finger of his left hand."'