"[Al-Safinat al-Jiyad] means: the swift horses. The singular form of it is "jawad" (swift). The "safin" (standing on three legs), in the Tafsir of Mujahid, is the horse when it raises one of its legs so that it rests on the edge of the hoof. They were presented to Sulayman, and they began running before him, such that one could not discern anything of them, neither little nor much, due to their speed. He began saying: "Bring them back to me," so that he might discern something of them."
﴿الصافنات الْجِيَاد﴾ يَعْنِي: الْخَيل السراع الْوَاحِد مِنْهَا: جواد , والصافن فِي تَفْسِير مُجَاهِد: الْفَرَسُ إِذَا رَفَعَ إِحْدَى رِجْلَيْهِ؛ حَتَّى تكون عَلَى طرف الْحَافِر. عُرِضتْ عَلَى سُلَيْمَان فجعلتْ تجْرِي بَين يَدَيْهِ فَلَا يستبين مِنْهَا قَلِيلا وَلَا كثيرا من سرعتها وَجعل يَقُولُ: ردُّوها عليّ؛ ليستبين مِنْهَا شَيْئا