In "Oedipus the King," why did the only surviving member of Laius's party beg Queen Jocasta to let him leave Thebes when he saw that Oedipus was king?
The first type of reason we can put forth for this has to do with the slave's motivations. Oedipus killed Laius. The slave is the only living witness to this. As a slave, he would have been absolutely powerless and is terrified that Oedipus will recognize him and put him to death. A king would have been within his rights to kill any slave on just a whim. There would have been no fear of negative consequences for doing so in light of both the power of a king and the low regard in which slaves were held in ancient society, in which legally they were property rather than people.
From a dramatic point of view, Sophocles needs to keep the slave alive in a credible fashion so that later in the play he can identify Oedipus as the killer of Laius.
Jocasta relates a story that, when the sole surviving member of Laius's party returned to Thebes after Laius had been slain on the road, he saw Oedipus was ruling Thebes in Laius's stead. At that point, the slave grasped Jocasta's hand and begged her to send him away to work in the pastures instead of the house so he can get as far away from Thebes as possible. Because the slave was always so good and loyal, Jocasta agrees to fulfill his request. The slave seems to have done this because he recognized Oedipus as the killer of Laius, and he perhaps was afraid that Oedipus would also recognize him or simply feared to live in a Thebes ruled by the man who murdered its former king.