The OEB currently reads:
"The people were amazed at his teaching, for he taught them like one who had authority, and not like the teachers of the law."
The use of "at" and "for" does not strike me as contemporary English usage. Recommed replacing with "by" and "because":
"The people were amazed by his teaching, because he taught them like one who had authority, and not like the teachers of the law."
The OEB currently reads:
"The people were amazed at his teaching, for he taught them like one who had authority, and not like the teachers of the law."
The use of "at" and "for" does not strike me as contemporary English usage. Recommed replacing with "by" and "because":
"The people were amazed by his teaching, because he taught them like one who had authority, and not like the teachers of the law."