"Itachi and Sasuke, Brothers" (兄と弟, Itachi to Sasuke) is chapter 220 of the original Naruto manga.
One day when they were younger, Sasuke accompanied Itachi on one of his training sessions. Impressed by Itachi's skills, Sasuke asked Itachi to teach him something, but Itachi, as always, refused by poking him on the forehead and promising to help him later. As they returned home, Sasuke marvelled at the Uchiha clan's accomplishments as explained to him by Itachi. When they encountered their father, Fugaku, he spoke to Itachi about an approaching mission. Itachi refused to take part, wishing to take part in Sasuke's Academy orientation. Seeing that Itachi was determined, Fugaku volunteered to go in his place.