士道は慌てて首を振った。いらぬことを言ってへそを曲げられ **てはことである** 。

Context: The boy 士道 was trying to persuade a girl. The girl hated men and
didn’t want to talk with 士道. If 士道 said anything amiss, the girl would get
sulky further.

Hi. What is the function or meaning of the bold part? Is it some fixed kind of
grammar pattern?

Thank you.
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2020-09-06T14:35:45.623
80517
2020-09-06T14:35:45.623
36662
question
clause-pattern
Meaning or function of てはことである?