In the novel To Kill a Mockingbird, what is one quote that Jem says that proves he is protective?

At the beginning of Chapter 4, Scout runs past the Radley's yard, and something catches her eye. Something about one of the two live oak trees at the edge of the Radley's yard attracts her attention. Scout finds some tinfoil sticking out of the knot-hole in one of the trees and reaches in to find two pieces of chewing gum. Scout immediately wants to put the sticks of gum into her mouth but remembers that she is in the Radley's yard. When Scout arrives home, she sniffs and licks the gum then crams it into her mouth. Jem returns home from school and asks Scout where she got the gum. Scout tells Jem that it was sticking out from the tree coming home from school and Jem yells at her to spit it out. Jem stamps his foot and says,

"Don't you know you're not supposed to even touch the trees over there? You'll get killed if you!" (Lee 45).

Jem portrays his overprotective nature by telling Scout to spit the "poisonous" gum out and gargle immediately. Jem is still naive and believes that the Radley trees are dangerous, and he was simply looking out for his younger sister.