Confused about having to bind VBO before editing VAO

I'm trying to draw a textured cube in OpengL. At first, I initialize VBO and VAO in the class constructor as follows.

Block::Block(...)
{
    glGenBuffers(1, &VBO);
    glGenVertexArrays(1, &VAO);
    //glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBindVertexArray(VAO);

    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *)0);
    glEnableVertexAttribArray(0);
    glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *)(3 * 
    sizeof(float)));
    glEnableVertexAttribArray(1);
    glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 8 * sizeof(float), (void *)(6 * 
    sizeof(float)));
    glEnableVertexAttribArray(2);
}

and in the method called renderBlock(), I render the cube like this

void Block::renderBlock()
{
    setMatrix();
    shader.use();
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBindVertexArray(VAO);

    glActiveTexture(GL_TEXTURE0);
    shader.setInt("tex", 0);

    shader.use();
    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
    glBindTexture(GL_TEXTURE_2D, texture);
    glBindVertexArray(VAO);

    glDrawArrays(GL_TRIANGLES, 0, 6);
}

and if I call the block.renderBlock(), the program will crash at glDrawArrays(GL_TRIANGLES, 0, 6);. The error message says that 0xC0000005: Access conflict occurred at read position 0x0000000000000000.. But if I uncomment the //glBindBuffer(GL_ARRAY_BUFFER, VBO); in constructer, the program will run successfully. It's very confusing to me. Why should I bind the VBO before I edit the VAO. Is there any connection between them？Any advice would be greatly appreciated.