contract/agreement_sale/views/agreement.xml

<?xml version="1.0"?>
<odoo>
<!-- Copyright 2018 Open Source Integrators
     License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl). -->

    <!-- Agreement Form View -->
	<record id="agreement_sale_form_view" model="ir.ui.view">
        <field name="name">agreement.form.view</field>
        <field name="model">agreement</field>
        <field name="inherit_id" ref="agreement.partner_agreement_form_view"/>
        <field name="arch" type="xml">
            <page name="signature" position="after">
                <page name="sales" string="Sales">
                    <group>
                        <group id="sale-left">
                            <field name="sale_id" readonly="1"/>
                        </group>
                        <group id="sale-right"/>
                    </group>
                </page>
            </page>
        </field>
    </record>

</odoo>