He was the one who asked for the marriage between his first daughter and Qin Wentian to the Qin Clan Manor because he needed their strength. Later, after the revelation of Autumn Snow talent, he betrayed the Qin Clan and the marriage engagement between Qin Wentian and Bai Autumn Snow to ally with their sworn enemy the Ye Clan to elevate the status of his clan and his own. He then wanted to kill Qin Wentian and destroy the whole Qin Clan to show that he cut ties with them and that they're ready to ally themselves with the Ye Clan by marriage. For what he did, he lose the trust and love of his second daughter Bai Qing, who despise him for his acts.
In the end, that failed and he got his cultivation crippled as punishment by Qin Wentian to atone for his sins. He then became a mortal and lost his long lifetime remaining, aging quickly.
He will always regret what he did that day, not only he got crippled, his second daughter left him and his first daughter didnt marry Qin Wentian and her talent was finally average. What glory could the Bai Clan have today if he had not betrayed the Qin Clan and his daughter had married Qin Wentian ...