Punches a boulder

“I didn’t want you to worry if we ran away, and then you came home, so I
waited for you.”
“Mm hmm.” His mother nodded, tears spilling down her face.
Eyes that had been narrowed with the tension of having to protect his little
brother relaxed to some degree. But this was fleeting. When he noticed
something closing in from behind his mother, those eyes quickly regained
their original grimness.

“Mom!” He practically threw Sasuke to his mother. And then he flew.
A boulder tossed into the air by Nine Tails shattered near their house, and
the pieces danced above their heads. One chunk was falling toward his
mother’s back. He looked down at her, clutching Sasuke to her chest. Her
surprised eyes chased after him; he could see the question there, her
wondering just what was happening to make Itachi leap up so suddenly.
The rock was enormous, large enough to easily crush a mother and her two
children.
“I’ll protect you,” he murmured. He clenched his fist tightly.
The physical arts of the ninja were not about strength. He might have been
a small child of five years, body as yet undeveloped, but as long as he
managed to knead his chakra properly, he could smash even this enormous
rock.
He brandished his fist high in the air. Chakra filled his arm, covering it in
faint blue flames.
The rock slammed into Itachi’s fist, and exploded with a shriek.
Even a child could effortlessly destroy boulders, as long as they simply
kept up their ninja training.
Showered in a rain of pebbles, he landed soundlessly on the ground.

Itachi Shinden: Book of Bright Light Chapter 1 Part 2