What is the ruling on an Jordanian (foreigner) leading the prayer when a Saudi is present, knowing that the Jordanian is known for his commitment to prayer and usually leads the people in the absence of the imam?

The most deserving person to lead the prayer (Imamah) is the one who best embodies the qualities mentioned in the Hadith: "The people are led by the one among them who is most knowledgeable of the Book of Allah..." So, if the person who comes forward to lead the prayer possesses these qualities more than the other attendees, then he is more entitled to lead, especially if he is diligent in observing prayers and leading the people. The prayer behind him is valid if he fulfills the conditions of Imamah. It is not a condition for the Imam to be a native citizen, as the only criterion for superiority in the sight of Allah is piety and righteous deeds.