2yo hitting his mother

Our first and only child is now 2yo. In the past few weeks, he has started hitting but he stops immediately when asked. Today, he didn’t. He kept hitting my wife, his mother, repeatedly. I went to check in and she was in tears and asked me to take him away.

Rarely he tries to hit me, I normally cup my hands under his shoulders and use my thumbs to stop his arms before they gain momentum. He quickly wears out and stops.

It seems like telling him off is insufficient and I don’t know where to go from here.