Joseph's master believed the accusation. Potiphar, it is likely, chose that prison, because it was the worst; but God designed to open the way to Joseph's honour. Joseph was owned and righted by his God.
He was away from all his friends and relations; he had none to help or comfort him; but the Lord was with Joseph, and showed him mercy. Those that have a good conscience in a prison, have a good God there.
God gave him favour in the sight of the keeper of the prison; he trusted him to manage the affairs of the prison. A good man will do good wherever he is, and will be a blessing even in bonds and banishment.
Let us not forget, through Joseph, to look unto Jesus, who suffered being tempted, yet without sin; who was slandered, and persecuted, and imprisoned, but without cause; who by the cross ascended to the throne.
May we be enabled to follow the same path in submitting and in suffering, to the same place of glory.