Surah 81. At-Takwir, Ayah 23

This is evidently a reference to the Prophet's vision of the Angel Gabriel which ended the break in revelation (fatrat al-wahy) mentioned in the introductory note to surah {74}. See also 53:5 ff. and the corresponding notes.

 This is first time the Prophet (ﷺ) saw Gabriel in his angelic form. He saw him a second time in heaven during the Night Journey. See 53:5-15.

Read along with this the whole passage in liii. 1-18 and notes there; specially n. 5092, where the two occasions are mentioned when there was a vision of inspiration: "For truly did he see, of the Signs of his Lord, the Greatest" (liii. 18).