Illuminate\Mail\PendingMail::send(): Argument #1 ($mailable) must be > of type Illuminate\Contracts\Mail\Mailable

This is the error I get when I am trying to send an email with Laravel:

Illuminate\Mail\PendingMail::send(): Argument #1 ($mailable) must be of type Illuminate\Contracts\Mail\Mailable, App\Http\Livewire\Auth\ResetPassword given, called in /Users/andreiraileanu/Development/Protein/app/Http/Livewire/Auth/ResetPassword.php

So I have a livewire component where I reset the user password:

<?php

namespace App\Http\Livewire\Auth;
 
use Livewire\Component;
use Illuminate\Support\Facades\DB;
use Illuminate\Support\Facades\Hash;
use Illuminate\Support\Str;
use Illuminate\Support\Facades\Mail;
use App\Models\User;

class ResetPassword extends Component
{
    public $email;
    public $phone;
    protected $user;

    protected $rules = [
        'email' => 'required|email',
        'phone' => 'required|digits:10',
    ];

    public function submit()
    {
        $this->validate();

        $this->user = User::where('email', $this->email)
                ->where('phone', $this->phone)
                ->first();
        if ($this->user) {
            
            \Debugbar::info('Identified User ID: '.$this->user->id);

            $this->user->password = Str::random(8);
            \Debugbar::info('New password is: '.$this->user->password);
            
            $this->user->password = Hash::make($this->user->password);
            $this->user->save();
            \Debugbar::info('Password saved!');
            
            Mail::to($this->user->email)->send(new ResetPassword($this->user));
        } else {
            $this->dispatchBrowserEvent('notify', ['content' => 'Adresa de email nu există sau numărul de telefon este incorect', 'type' => 'error']);
            \Debugbar::error('Wrong email and/or phone number.');
        }
    }

    public function render()
    {
        return view('livewire.auth.reset-password');
    }
}

In this component I have a line where I try to email the new password like this Mail::to($this->user->email)->send(new ResetPassword($this->user)); but I get the error above.

This is what my Mailable looks like:

<?php

namespace App\Mail;

use Illuminate\Bus\Queueable;
use Illuminate\Contracts\Queue\ShouldQueue;
use Illuminate\Mail\Mailable;
use Illuminate\Queue\SerializesModels;
use App\Models\User;

class ResetPassword extends Mailable
{
    use Queueable, SerializesModels;

    protected $user;

    public function __construct(User $user)
    {
        $this->user = $user;
    }

    public function build()
    {
        return $this->subject('Order Shipped')
            ->view('emails.auth.reset-password');
    }
}

What am I doing wrong? Never encountered this error before.