Musnad Ahmad 32:752

'Abd al-Razzaq narrated to us, Ma'mar informed us, from Qatadah, from Anas, or from al-Nadr ibn Anas, from Anas, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Indeed, Allah has promised me that He will cause four hundred thousand of my nation to enter Paradise." Abu Bakr said: "Increase us, O Messenger of Allah." He said: "Like this," and he gathered his palm. He said: "Increase us, O Messenger of Allah." He said: "Like this." Then Umar said: "That is enough for you, O Abu Bakr." Abu Bakr said: "Leave me, O Umar. What is it to you if Allah causes us all to enter Paradise?" Umar said: "Indeed, if Allah wills, He can cause all His creation to enter Paradise with a single handful." The Prophet (peace and blessings of Allah be upon him) said: "Umar has spoken the truth."