JSFiddle - React, Tailwind, and code Playground

by rough cheap

HTML

<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.6.1/css/all.css">
<input type="button" class="btn-search" value="検索">
<h3>
test
</h3>

CSS

input[type="button"] {
}

.btn-search::before {
  font-family: "Font Awesome 5 Free";
  content: "\f00c";
  font-weight: 900;
  padding: 5px;
  color: #f89174;
}

h3:before {
  font-family: "Font Awesome 5 Free";
  content: "\f00c";
  font-weight: 900;
  padding-right : 5px;/*文字との隙間*/
  color: #f89174;/*アイコンの色*/
}