Wrap your resource in a drawable that defines your desired size similar to:
<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >
<item
android:drawable="@drawable/icon"
android:width="@dimen/icon_size"
android:height="@dimen/icon_size"
/>
</layer-list >
After that, use this drawable in your android:drawableLeft
tag