on the house

If you have something on the house, it is given to you free by a business.

由商家免费提供的

All the drinks were on the house.

所有的饮料都是免费的。

The owner knew about the engagement and brought them glasses of champagne on the house.

店主知道了他们订婚的事，便免费请他们喝了几杯香槟酒。