I have two divs here, the section on the left with "Sumar" and "Alumno", and the section on the right with the form. 

When there is a validation issue with the form content, messages appear making the right div resize to fit the content. The left div does not resize to match:

How do I make the left div resize to match the right div at all times?
[Update]
View:
@model Biblioteca.Models.SapDepoViewModel
 @{
    ViewBag.Title = "SapDepo";
 }
 <body class="background-greenbkg">
<div class="container bold-titty" id="wite-color">               
    <div class="col-md-12">
        <h2 class="cajita-titulo textofont"><i class="fa fa-bolt" style="color:yellow"></i>  Sap | Depósito <i class="fa fa-money" style="color:green"></i> </h2>
    </div>
    <div class="hidden-xs hidden-sm col-md-1 col-md-push-4 margin-top-bot2 colorcajitaizqsap">
        <div class="row height-sidetitle-sap padding-edit">
            <i class="fa fa-dollar"></i>
            <p id="fontiponki">Sumar</p>
            <p id="minifont">Alumno</p>
        </div>
    </div>
        @using (Html.BeginForm("SapDepo", "Alumnos", FormMethod.Post))
        {
            @Html.AntiForgeryToken()
            @Html.ValidationSummary(true, "", new {@class = "text-danger"})
            @Html.HiddenFor(x => x.AlumnosId)
            <div class=" hidden-xs hidden-sm col-md-push-4 col-md-4 cajita">
                <section id="SapDepoAlumnos" >
                    <div class="form-group">
                        <div class="row">                                
                            <div class= "col-md-push-1 col-md-5">
                                @Html.LabelFor(x => x.Sap, htmlAttributes: new {@class = "control-label col-md-2"})
                            </div>
                            <div class="col-md-6">
                                @Html.EditorFor(x => x.Sap, new {htmlAttributes = new {@class = "form-control"}})
                                @Html.ValidationMessageFor(x => x.Sap, "", new {@class = "text-danger"})
                            </div>
                        </div>
                    </div>
                    <div class="form-group">
                        <div class="row">
                            <div class="col-md-push-1 col-md-5">
                                @Html.LabelFor(x => x.Deposito,"Depósito", htmlAttributes: new {@class = "control-label col-md-2"})
                            </div>
                            <div class="col-md-6">
                                @Html.EditorFor(x => x.Deposito, new {htmlAttributes = new {@class = "form-control"}})
                                @Html.ValidationMessageFor(x => x.Deposito, "", new {@class = "text-danger"})
                            </div>
                        </div>
                    </div>
                </section>
                <div class="form-group">
                    <div class="row">
                        <div class="col-md-offset-2 col-md-8">
                            <input type="submit" value="Agregar" class="btn btn-success" style="border-radius: 4px; width: 100%" />
                        </div>
                    </div>
                </div>
                <div class="form-group">
                    <div class="row">
                        <div class="col-md-offset-2 col-md-8">
                            <a href="/Alumnos/Index"> <input type="submit" value="Cancelar transacción" class="btn btn-danger" style="border-radius: 4px; width: 100%" /></a>
                        </div>
                    </div>
                </div>
            </div>
        }
    </div>
CSS of divs:
 //Right side
 .margin-top-bot2 {
     margin-top: 61px;
     margin-bottom: 10px;
 }
 .colorcajitaizqsap {
     /*background-color: rgba(250, 255, 0,0.2);*/
     background: repeating-linear-gradient(
   45deg,
  rgba(107, 153, 85, 0.65),
  rgba(107, 153, 85, 0.65) 10px,
  rgba(0, 54, 41, 0.65) 10px,
  rgba(0, 54, 41, 0.65) 20px
  );
     border-radius: 10px 0 0 10px;
       }
.height-sidetitle-sap {
     height: 225px;
}
 .padding-edit {
    padding-left: 20px;
   font-size: 60px;
}
//Left side
.cajita {
padding-top: 30px;
color: #ffffff;
text-align: center;
background-color: rgba(0, 0, 0,0.3);
box-shadow: 0 3px 10px 0 rgba(0,0,0,0.1);
-webkit-border-radius: 3px;
-moz-border-radius: 3px;
border-radius: 0 10px 10px 0;
margin-top: 60px;
}
 
     
    