Phaedo

Plato's Phaedo is one of the great dialogues of his middle period, along with the Republic and the Symposium. The Phaedo, which depicts the death of Socrates, is also Plato's seventh and last dialogue to detail the philosopher's final days (the first six being Theaetetus, Euthyphro, Sophist, Statesman, Apology, and Crito).

In the dialogue, Socrates discusses the nature of the afterlife on his last day before being executed by drinking hemlock. Socrates has been imprisoned and sentenced to death by an Athenian jury for not believing in the gods of the state and for corrupting the youth of the city. The dialogue is told from the perspective of one of Socrates' students, Phaedo of Elis. Having been present at Socrates' death bed, Phaedo relates the dialogue from that day to Echecrates, a fellow philosopher. By engaging in dialectic with a group of Socrates' friends, including the Thebans Cebes and Simmias, Socrates explores various arguments for the soul's immortality in order to show that there is an afterlife in which the soul will dwell following death. Phaedo tells the story that following the discussion, he and the others were there to witness the death of Socrates. Source - Wikipedia