Hilary of Poitiers
Catena Aurea · Matthäusevangelium 27
And they crucified him, and parted his garments, casting lots: that it might be fulfilled which was spoken by the prophet, They parted my garments among them, and upon my vesture did they cast lots. And sitting down they watched him there; And set up over his head his accusation written, THIS IS JESUS THE KING OF THE JEWS. Then were there two thieves crucified with him, one on the right hand, and another on the left.
Or otherwise; Two thieves are set up on His right and left hand, to signify that the entire human race is called to the Sacrament of the Lord’s Passion; but because there shall be a division of believers to the right, and unbelievers to the left, one of the two who is set on His right hand is saved by the justification of faith.