The former Trump national security adviser will be peppered with questions about Signal in his confirmation hearing for United Nations ambassador.

Waltz is a former Green Beret and Florida representative who resigned from Congress to join the Trump administration. He served as national security adviser for roughly three months. Trump reshuffled his team and named Secretary of State Marco Rubio acting national security adviser on May 1.

Former national security adviser Mike Waltz will testify before the Senate on Friday morning on his nomination for U.S. ambassador to the United Nations. Waltz, who left his previous post in May after controversy surrounding the Trump administration’s use of the Signal messing app,