use Sahel font for Farsi as suggested by iriman

_layouts/default.html

@@ -17,6 +17,9 @@
     <link rel='shortcut icon' href='{{site.baseurl}}/img/favicon.ico' type='image/x-icon' />
     <link href="https://code.jquery.com/ui/1.9.2/themes/base/jquery-ui.css" rel="stylesheet" >
     <link href='https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,700,400italic|Quattrocento+Sans:400,700&subset=latin,latin-ext' rel='stylesheet' type='text/css'>
+    {% if page.lang == "fa" %}
+    <link href="https://cdn.jsdelivr.net/gh/rastikerdar/[email protected]/dist/font-face.css" rel="stylesheet" type="text/css" />
+    {% endif %}
     <script src="{{ site.baseurl }}/vendor/jquery-1.8.2.min.js"></script>
     <script src="{{ site.baseurl }}/vendor/jquery-ui-1.9.2.custom.js"></script>
     <script>

style-rtl.css

@@ -257,6 +257,18 @@ blockquote p:before {
   -o-transition: all 200ms linear;
 }
 
+/* font configuration for Farsi */
+[lang="fa"] body,
+[lang="fa"] .doc ol > li:before,
+[lang="fa"] .doc ul > li:before,
+[lang="fa"] .doc  ul li,.doc ol li, .doc p,
+[lang="fa"] blockquote p,
+[lang="fa"] .searchbox input,
+[lang="fa"] .ui-menu-item {
+  font-family: Sahel, sans-serif !important;
+  font-size: 1em;
+}
+
 /* --------------------------------------------------------
   Layout
 -------------------------------------------------------- */