Sending a text between two Arduino (wired)

We tried using the wire examples: Arduino1 as the master writer and Arduino2 as the slave receiver.
as the exampled worked we got the hello looping on serial monitor of Arduino2 so we try to modify the program like this:

#include <Wire.h>
char rx_byte;
void setup()
{
  Wire.begin(); // join i2c bus (address optional for master)
  
}


void loop()
{
  Wire.beginTransmission(4); // transmit to device #4
  Wire.write(rx_byte);        // sends five bytes 
  Wire.endTransmission();    // stop transmitting

  delay(500);
}

I don't know to much of the libraries function so I just fooled around with it.