How can the boss send a text message to express his condolences when he has a car accident?

You should go to the hospital yourself and wish the boss a speedy recovery. If you have to send a short message, you can send it like this:

1, the employees of the company are very sad about your misfortune. You are our eternal theme! God bless you! A thousand words turn into blessings: I hope you will recover soon! We will all love you more than before!

I was shocked to hear that you had an unfortunate car accident. I specially made a medicine for you, which contains: one gram of sunshine, two grams of fresh air, three grams of happy mood, and one kilogram of love and blessing from all staff. Take the pill that is full of deep love and deep blessing from all employees! You will get better soon!