A yoke s a wooden harness for two beasts working together, with the word “yoke” being an Indo-European word for “joining two.”
So, Jesus is here comparing himself to an old ox on one side of the yoke. He is inviting you to slip in next to him to achieve a happy, peaceful existence. You will do that by learning from him to never fight against the directions God has set for you.
The book of Revelation refers to Jesus simply as “The Lamb” and he is a lamb all through the Bible, but the image of the ox can be even more appealing. I found it so in my twelve years in a country parish in Korea. Looking lovingly on such a beast, I would see his blend of docility and strength more Christ-like than any thing a lamb has to offer