Sahih Bukhari Volume 5, Book 58, Hadith Number 158.

Narated By Qais bin Ubad : While I was sitting in the Mosque of Medina, there entered a man (Abdullah bin Salam) with signs of solemnity over his face. The people said, “He is one of the people of Paradise.” He prayed two light Rakat and then left. I followed him and said, “When you entered the Mosque, the people said, ‘He is one of the people of Paradise.’ ” He said, “By Allah, one ought not say what he does not know; and I will tell you why. In the lifetime of the Prophet I had a dream which I narrated to him. I saw as if I were in a garden.” He then described its extension and greenery. He added: In its center there was an iron pillar whose lower end was fixed in the earth and the upper end was in the sky, and at its upper end there was a (ring-shaped) hand-hold. I was told to climb it. I said, “I can’t.” “Then a servant came to me and lifted my clothes from behind and I climbed till I reached the top (of the pillar). Then I got hold of the hand-hold, and I was told to hold it tightly, then I woke up and (the effect of) the hand-hold was in my hand. I narrated al I that to the Prophet who said, ‘The garden is Islam, and the hand-hold is the Most Truth-worthy Hand-Hold. So you will remain as a Muslim till you die.” The narrator added: “The man was ‘Abdullah bin Salam.”