Surah Ar-Rum 30:3

فِىٓ أَدْنَى ٱلْأَرْضِ وَهُم مِّنۢ بَعْدِ غَلَبِهِمْ سَيَغْلِبُونَ

In the nearest land. But they, after their defeat, will overcome

Translation: Saheeh International

Tafsir

in the nearer part of the land that is in the Byzantine land that lies nearest to Persia in Mesopotamia al-Jazīra. There the two armies met and the Persians were the ones who had begun the invasion. …

Excerpt from Tafsir al-Jalalayn, commentary on 30:3, via Quran.com. The reader has the full commentary and 9 more tafsirs.