WASHINGTON — The F.B.I. director, James B. Comey, provided his first public explanation Wednesday of why he revealed days before the election that he had reopened the investigation into Hillary Clinton’s emails, saying he could not risk concealing newfound information from Congress.

In nearly four hours of testimony before the Senate Judiciary Committee, Mr. Comey was also asked about the F.B.I.’s investigation into links between President Trump’s associates and the Russian government, among other issues.

Here are five highlights from Mr. Comey’s testimony:

1. He’d Do It All Over Again

Mr. Comey was adamant that if he had to choose again, he would still have informed Congress 10 days before the election that he had reopened the investigation into Mrs. Clinton’s emails. His decision prompted a flood of news coverage, and supporters of Mrs. Clinton later accused him of costing her the presidency.

“I could see two doors, and they were both actions,” Mr. Comey said. “One was labeled ‘Speak’; the other was labeled ‘Conceal.’”