Question: where did the ashes from ash wednesday originate
[{'answer': 'Pope Gregory I the Great', 'provenance': [{'wikipedia_id': '170388', 'title': 'Ash Wednesday', 'start_paragraph_id': 15, 'start_character': 462, 'end_paragraph_id': 15, 'end_character': 486, 'bleu_score': 1.0, 'section': 'Section::::Observances.:Ashes.\n'}]}, {'answer': "burning palm leaves from the previous year 's Palm Sunday celebrations"}, {'provenance': [{'wikipedia_id': '170388', 'title': 'Ash Wednesday', 'start_paragraph_id': 15, 'start_character': 0, 'end_paragraph_id': 15, 'end_character': 1009, 'bleu_score': 0.9280319125710781, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6553675717773043249}, 'section': 'Section::::Observances.:Ashes.\n'}]}, {'provenance': [{'wikipedia_id': '170388', 'title': 'Ash Wednesday', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 326, 'bleu_score': 0.9036816878108531, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6553675717773043249}, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '170388', 'title': 'Ash Wednesday', 'start_paragraph_id': 34, 'start_character': 0, 'end_paragraph_id': 34, 'end_character': 969, 'bleu_score': 0.8664362363793431, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6553675717773043249}, 'section': 'Section::::Biblical significance of ashes.\n'}]}, {'provenance': [{'wikipedia_id': '170388', 'title': 'Ash Wednesday', 'section': 'Section::::Observances.:Ashes.\n', 'start_paragraph_id': 15, 'end_paragraph_id': 15, 'meta': {'evidence_span': ['Ashes are ceremonially placed on the heads of Christians on Ash Wednesday, either by being sprinkled over their heads or, in English-speaking countries, more often by being marked on their foreheads as a visible cross. The words (based on Genesis 3:19) used traditionally to accompany this gesture are, ""Memento, homo, quia pulvis es, et in pulverem reverteris."" ("Remember, man, that thou art dust, and to dust thou shalt return.") This custom is credited to Pope Gregory I the Great (c. 540604). In the 1969 revision of the Roman Rite, an alternative formula (based on Mark 1:15) was introduced and given first place "Repent, and believe in the Gospel" and the older formula was translated as "Remember that you are dust, and to dust you shall return." The old formula, based on the words spoken to Adam and Eve after their sin, reminds worshippers of their sinfulness and mortality and thus, implicitly, of their need to repent in time. The newer formula makes explicit what was only implicit in the old.', 'The words (based on Genesis 3:19) used traditionally to accompany this gesture are, ""Memento, homo, quia pulvis es, et in pulverem reverteris."" ("Remember, man, that thou art dust, and to dust thou shalt return.") This custom is credited to Pope Gregory I the Great (c. 540604).']}}]}]