Source and decoding
אין בודקין לא לאור החמה, ולא לאור הלבנה, ולא לאור האבוקה, אלא לאור הנר
One does not search by sunlight, nor by moonlight, nor by a torch, but only by candlelight.
The baraita limits the search to a candle. Later the sugya (ח ע״א (8a)) offers reasons: Rav Nachman bar Yitzchak says a candle can enter holes and crevices, Rav Zevid says its light is before the searcher, and Rav Papa and Ravina add distinctions. Without deciding among the reasons here, the baraita clearly names a defined light source and not just any light.