The Book of Tribulations and Portents of the Last Hour
وَحَدَّثَنَا أَبُو غَسَّانَ الْمِسْمَعِيُّ، حَدَّثَنَا مُعْتَمِرٌ، عَنْ أَبِيهِ، عَنْ مَعْبَدٍ، عَنْ أَنَسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " بُعِثْتُ أَنَا وَالسَّاعَةُ كَهَاتَيْنِ " . قَالَ وَضَمَّ السَّبَّابَةَ وَالْوُسْطَى .Anas reported Allah's Messenger (ﷺ) as saying:I and the Last Hour have been sent like this and (he while doing it) joined the forefinger with the middle finger
From Sahih Muslim, whose reports the scholars accept as authentic.