In the preceding chapter Sophar had already consented to the opinion of Job, at least in part. He had affirmed that sins were punished after death, although he still retained in this his own opinion that sins were also punished temporally in this life. For this reason Job has some hope of converting them completely to the true opinion. So he first humbly invites his friends to pay attention when he says, "Listen, I beseech you, to my words." Since up to this time they had heard his words with some mockery, he says then, "and do penance," about the fact that you have jeered at my words or have contradicted the truth.
Source: Commentary on Job