This hadith has been reported by Sahl bin 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).
Explanation & Benefits
Shaykh Maulana Abdul Aziz Alvi
Hadith Commentary: Benefits and Issues: Just as there is no gap between the index finger and the middle finger, likewise, there is no gap between me and the Hour (Qiyamah); the Hour will come during the era of my Prophethood.
Source: Tuhfat al-Muslim: Commentary on Sahih Muslim, Page: 7403