In one narration the words are: "Which (light) will be running before them and on their right."
Ahmad recorded this narration, and its narrators are the narrators of the Sahih except for Ibn Lahi'ah, who is da'if (weak), though he has also been declared trustworthy.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب البعث / 18362