1. Show validation error

 <form id="settings-profile" method="post" action="">


    <div class="mb-6">
        <label for="firstName" class="text-sm font-medium text-gray-900 block mb-2 dark:text-gray-300">First Name</label>

        <input type="firstName" id="firstName" name="firstName" value=""  required>

        @ if($errors->has('firstName'))
            <div class="error text-red-500 text-xs">{{ $errors->first('firstName') }}</div>
       @endif
    </div>

    <div class="mb-6">
        <label for="lastName" class="text-sm font-medium text-gray-900 block mb-2 dark:text-gray-300">Last Name</label>

        <input type="lastName" id="lastName" name="lastName" value=""  required>

        @if($errors->has('lastName'))
            <div class="error text-red-500 text-xs">{{ $errors->first('lastName') }}</div>
        @endif
    </div>
</form>

Laravel controller

$request->validate([
        'title' => 'required|unique:posts|max:255',
        'body' => 'required',
    ]);


if($validate->fails()) {
  return Redirect::back()->withErrors($validate);
}

2. show old form values and default form values

<form id="settings-profile" method="post" action="">


<div class="mb-6">

    <label for="firstName" class="text-sm font-medium text-gray-900 block mb-2 dark:text-gray-300">First Name</label>

    <input type="firstName" id="firstName" name="firstName" value="{{old('firstName', $profile->lastName)}}" required>

    @if($errors->has('firstName'))
        <div class="error text-red-500 text-xs">{{ $errors->first('firstName') }}</div>
    @endif

</div>

<div class="mb-6">
    
    <label for="lastName" class="text-sm font-medium text-gray-900 block mb-2 dark:text-gray-300">Last Name</label>

    <input type="lastName" id="lastName" name="lastName" value="{{old('lastName'}}" required>

    @if($errors->has('lastName'))
        <div class="error text-red-500 text-xs">{{ $errors->first('lastName') }}</div>
    @endif

</div>
</form>

In controller

if($validate->fails()) {
   return Redirect::back()->withInput()->withErrors($validate);
}

In view

@if (count($errors) > 0)
            <div class="alert alert-danger">
                <ul>
                     @foreach ($errors->all() as $error)
                      <li>{{ $error }}</li>
                      @endforeach
                </ul>
            </div>
            @endif