JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="nav">
  <li class='phone'><a>+7123123123132</a></li>
</ul>

CSS

.phone {
  position: relative;
  padding-left: 20px;
}

.phone:before {
  content: '';
  position: absolute;
  left: 0;
  top: 0;
  width: 16px;
  height: 16px;
  background: url(https://use.fontawesome.com/releases/v5.0.13/svgs/solid/phone.svg);
  background-size: 16px 16px;
}

.nav {
  margin: 0;
  padding: 0;
  list-style: none;
}