After greetings I wanted to know if I committed a sin. My father and I disagreed on something, I wanted to go to a sermon which was being held on our neighborhood and on this sermon it was all about Islamic knowledge, but suddenly my father refused for me to go just because he disliked those people. I didn't listen to him and went instead. Did I commit a bad act am I now a sinner. Please reply to me as soon as possible. Because he's angry and don't talk to me nowadays.

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.

It is an obligation on you to obey your parents unless they order you to disobey Allaah as there should be no obedience to a creature in disobeying the Creator. So if the lecture that you mentioned in the question was about a knowledge that is obligatory upon every Muslim to know then there was no harm on you to attend it as it is an obligation to seek the knowledge that is obligatory upon every person to know; and it would have been a sin not to attend this kind of lecture. Indeed, there is no obedience to a person who orders someone to sin or repels him from performing an obligation.

However, if the lecture was a general one and if by not attending it, one did not miss an obligatory knowledge then it was not permissible for you to attend such a lecture without the permission of your father, and if you did attend without his permission, you have to repent to Allaah.

Saying that your father does not like 'those people', if it is because of their religion, righteousness and their adherence to the Islamic Law, then he is in a very serious state as loving the people of righteousness is evidence of having faith and hating them is evidence of hypocrisy; we seek refuge in Allaah from it. Actually, whoever loves Allaah as he should, he automatically would love those who are loved by Allaah and those who love Allaah, and would hate His enemies. However, if your father hates them because they are innovators and the like, then there is no harm on him for this. In fact Imaam At-Tahaawi said: 'We love just and trustworthy people and we hate unjust and disloyal people.'

Finally, we advise you to seek to please your father as much as you can mainly if you were wrong in going to the lecture. The Prophet said: "The pleasure of Allaah is attained by pleasing parents, and the wrath of Allaah is ensued by angering parents." [Al-Bazzaar]

Allaah Knows best.