I have a bank account in a conventional bank in order to be able to receive my salary from my office, and it is mandatory. I have to go to the bank for my personal and official purposes. Sometimes, they offer me tea, but I always politely refuse. Today, however, they requested me to take tea in such way that it was hard to refuse it, so I accepted it. Note that the bankers are Muslim and that they spend on this from an official fund. Was it sinful for me to accept it, and what can I do now?

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, sallallaahu ʻalayhi wa sallam, is His slave and Messenger. 

There is no harm in drinking what was offered to you in the usurious bank. Shaykh Ibn ʻUthaymeen wrote:

“One is allowed to accept the invitation of someone who deals with interest unless refusing his invitation constitutes a valid benefit. The evidence for this is that the Messenger of Allaah, sallallaahu ʻalayhi wa sallam, accepted the invitation of the Jews, while he was the master of the God-fearing, and it was known that the Jews consumed interest and devoured people's wealth unjustly. Nevertheless, he accepted their invitations because the prohibition of the unlawful money is related to the person’s liability, not to the money itself, unless the money is unlawful in and of itself. In this case, such unlawful money is prohibited for its owner and anyone else. This is the basic principle that incorporates all the relevant evidence in this regard. An example of money that is itself unlawful is if a person were to steal some money and give it to another person. It is not permissible for that other person to accept it while knowing that it is stolen because this money is unlawful in and of itself. This is contrary to the case when the person earns the money in an unlawful manner (such as through interest). The prohibition of such ill-gotten money is related to the person’s liability, and not to the money itself. If this money is given to another person through lawful means, then it is lawful for him to take it.” [Fataawa ʻala Ad-Darb]

Allaah knows best.