From Sahih Muslim (Hadith 7403):
This hadith has been reported by Sahl b. Sa'd that he heard Allah's Messenger (ﷺ) as saying:I and the Last Hour are (close to each other) like this (and he, in order to explain it) pointed (by joining his) forefinger, (one) next to the thumb and the middle finger (together)
Reference: Muslim 7403