How to get authenticate to work?

In my SessionController, I tried to authenticate the user but it's
failing to authenticate even though I output the information and it's
all correct.I'm following this tutorial:

Below is my code:

def create
    user = User.find_by(email: params[:email].downcase)
    if user && user.authenticate(params[:password])
        session[:user_id] =
        flash[:notice] = "Welcome back, #{}!"
        redirect_to user
    else[:alert] = "Invalid email/password combination!
#{}, #{}, #{params[:password]}"
        render :new
def destroy
    session[:user_id] = nil
    redirect_to :new

The authenticate works fine in rails console but not when the rails
server. The problem is with this line
user.authenticate(params[:password]) of code.

Any help is much appreciated.

The password is in the session cookie:

if user && user.authenticate(params[:session][:password])