All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
If your father works in a commercial insurance company, then the decision and Fataawa of the Islamic Fiqh council and the Fataawa of the majority of contemporary scholars is that all kinds of commercial insurance are forbidden as they are based on undefined contracts, gambling, usury and interest and taking people's money without right. Therefore, it is forbidden to work in such companies, and the money obtained from this work is forbidden money because it is taken in an unlawful way from a forbidden work, whether this money is obtained in one year or in 25 years.
However, if he does not know that this kind of work is forbidden, we hope that there is no harm on him to consume this money after knowing that it is forbidden and after repenting to Allaah. Allaah says about the money that is obtained from usury (which means): {So whoever has received an admonition from his Lord and desists may have what is past, and his affair rests with Allaah. But whoever returns [to dealing in interest or usury], those are the companions of the Fire; they will abide therein.}[Quran 2:275]. Nonetheless, it is better for him to spend this money in charitable fields.
If he took the wages from his work while knowing that it is forbidden to do so, then first he has to repent to Allaah and then get rid of the remainder of this money by spending it in charitable fields, in the public interest and on poor and destitute people, but he should not spend it on himself or on the people he is obliged to provide for unless he is poor; in which case he should take only according to what he and the people he is obliged to provide for need.
However, if the company in which your father works is not a commercial insurance but an Islamic cooperative insurance, then there is no harm in working in such a company if it abides by the Islamic requirements.
In case the work of your father is forbidden according to what we have illustrated, then we advise you to take it easy when advising him, and you should do so in a good and soft manner and seek the help of pious and righteous people who know your father [as they might influence him and he would take heed thereof].
Finally, we ask Allaah with His Beautiful Names and Attributes to enable you and your father to do what He likes and He is pleased with.
Allaah knows best.