What is the rhetorical secret behind defining "the city" (البلد) in Surat Ibrahim and indefinining "a city" (بلدًا) in Surat Al-Baqarah in the supplication of Abraham (peace be upon him)?

The indefiniteness of “balad” (town/city) in Surat Al-Baqarah is because the supplication was for an empty place to become a safe town. As for its definiteness in Surat Ibrahim, it is because the supplication was made after the place had already become a prosperous town.