The first of mankind to enter Paradise will be our Prophet Muhammad (saw) and the first nation to enter Paradise will be his ummah. The first member of this ummah to enter will be Abu Bakr as-Siddiq (ra).
Ibn Katheer quotes a number of Hadith [an-Nihayah, 2/213] that state this such as the report of Muslim from Anas (ra) according to which the Messenger of Allah (saw) said, “I will be the first one to knock at the gates of Paradise”.
Muslim also reported from Anas that the Messenger of Allah (saw) said: “I will come to the gates of paradise and ask for it to be opened. The gatekeeper will ask, “Who are you?” I will say, “Muhammad”. The gatekeeper will say, “I was ordered not to open the gate for anyone else before you””.
al-Bukhaari, Muslim and an-Nasaa’ee report from Abu Hurayrah (ra) that the Prophet (saw) said: “We are the last, but we will be the first on the Day of Resurrection. We will be the first of mankind to enter Paradise”.
Abu Dawood reports from Abu Hurayrah (ra) that the Prophet (saw) said, “Jibreel came to me, and showed me the gate of Paradise through which my ummah will enter”. Abu Bakr said, “O Messenger of Allah (saw), would that I had been with you to see it!”. The Messenger of Allah (saw) “But you, O Abu Bakr, will be the first of my ummah to enter Paradise”.