Hadith: In the time of the Prophet (may Allah's peace and blessings be upon him) we would not find such food except rarely. So if we found it, we had no napkins except our palms, forearms, and feet. Then we would pray without making (a new) ablution

عن سعيد بن الحارث: أنه سأل جابرا رضي الله عنه عن الوضوء مما مَسَّتِ النارُ، فقال: لا، قد كنا زمن النبي - صلى الله عليه وسلم - لا نجد مثل ذلك الطعام إلا قليلا، فإذا نحن وجدناه، لم يكن لنا مَنَادِيلُ إلا أَكُفَّنَا، وسَوَاعِدَنَا، وأَقْدَامَنَا، ثم نصلي ولا نتوضأ.
[صحيح] - [رواه البخاري]

Sa‘īd ibn al-Hārith asked Jābir (may Allah be pleased with him) on making ablution after eating food that was touched by fire. He said: "No. in the time of the Prophet (may Allah's peace and blessings be upon him) we would not find such food except rarely. So if we found it, we had no napkins except our palms, forearms, and feet. Then we would pray without making (a new) ablution.''
[Authentic hadith] - [Narrated by Bukhari]

Explanation

Sa‘īd ibn al-Hārith asked Jābir ibn ‘Abdullāh (may Allah be pleased with him) about making ablution after eating food that was touched by fire, i.e. cooked or grilled or the like, whether it was obligatory or not? Jābir replied that it was not obligatory. Then he cited evidence for that. He said that during the lifetime of the Prophet (may Allah's peace and blessings be upon him) such food was rare. If they happened to find it and eat it, they didn't have napkins to wipe away the grease; rather, they would lick their fingers then rub them in their palms, forearms, and feet. Then they would pray without making a new ablution.