Jamieson, Fausset and Brown on Ezekiel 20:5-6

5-6. The thrice lifting up of God's hand (the sign of His oath, Re 10:5, 6; Ex 6:8, Margin; Nu 14:30; to which passages the form of words here alludes) implies the solemn earnestness of God's purpose of grace to them.

made myself known unto them--proving Myself faithful and true by the actual fulfilment of My promises (Ex 4:31; 6:3); revealing Myself as "Jehovah," that is, not that the name was unknown before, but that then first the force of that name was manifested in the promises of God then being realized in performances.