stock_display_sale_id/stock_view.xml

<?xml version="1.0" encoding="utf-8"?>

<!--
    Copyright (C) 2014 Akretion (http://www.akretion.com/)
    @author Alexis de Lattre <alexis.delattre@akretion.com>
    The licence is in the file __openerp__.py
-->

<openerp>
<data>


<record id="view_picking_form" model="ir.ui.view">
    <field name="name">display.sale_id.in.outgoing.picking.form</field>
    <field name="model">stock.picking</field>
    <field name="inherit_id" ref="stock.view_picking_form" />
    <field name="arch" type="xml">
        <field name="origin" position="after">
            <field name="sale_id" readonly="1" attrs="{'invisible': [('picking_type_code', '!=', 'outgoing')]}"/>
        </field>
    </field>
</record>


</data>
</openerp>