The 1922 League of Nations Mandate Document:
Article 2 The Mandatory shall be responsible for placing the country under such political, administrative and economic conditions as will secure the Mandate for Palestine – League of Nations (12 August 1922) establishment of the Jewish national home, as laid down in the preamble, and the development of self-governing institutions, and also for safeguarding the civil and religious rights of all the inhabitants of Palestine, irrespective of race and religion.
Article 5 The Mandatory shall be responsible for seeing that no Palestine territory shall be ceded or leased to, or in any way placed under the control of, the Government of any foreign Power.