JSFiddle - React, Tailwind, and code Playground

HTML

<div id='button'>
    <div class='icon'></div>
    <span>Send Email</span>
</div>

CSS

#button {
    width: 270px;
    height: 50px;
    font-size: 1.4em;
    color: #333;
    background-color: #555;
    position: relative;
}
#button > .icon {
    width: 61px;
    height: 39px;
    background-image: url('http://i55.tinypic.com/2agsutj.png');
    background-repeat: no-repeat;
    background-position: 0px 0px;
    position: absolute;
    left: 40px;
    top: 5px;
}
#button > span {
    position: absolute;
    left: 130px;
    top: 10px;
}
#button:hover {
    color: #fff;
    cursor: pointer;
}

JavaScript

$(function() {
    $('#button').hover(function() {
        $('#button > .icon').css('background-position', '0px -39px');
    }, function() {
        $('#button > .icon').css('background-position', '0px 0px');
    });
});