If it is insisted that the reference here should only be to a ruler...

If it is insisted that the reference here should only be to a ruler, then why should it not be taken to mean a companion of Amir al-mu'minin who had been the head of a Province such as Salman al-Farisi for whose burial Amir al-mu'minin went to al-Mada'in; and it is not implausible that Amir al-mu'minin might have uttered these words after his burial by way of comments on his life and way of governance. However, to believe that they are about Caliph `Umar is without any proof.