In a situation where a Muslim is involved in a business partnership and their partner proposes a new venture that conflicts with Islamic ethics—such as dealing with interest (riba) or gambling (maysir)—it is important for the Muslim partner to take a principled stance in order to protect their religious integrity.

Here are the steps the Muslim partner can take:

1. **Clarify Islamic Teachings**: The first step is to communicate with the business partner about the un-Islamic nature of the proposed venture. This can involve explaining that both interest-based transactions and gambling are prohibited in Islam (haram). It is important to approach the conversation with respect and clarity, citing relevant Islamic sources (Quran and Hadith) to support the stance.

2. **Seek an Alternative**: Propose a more ethical and Islamically permissible alternative. For instance, if the venture involves riba, suggest restructuring the business model to avoid interest-based transactions. If it involves gambling, suggest shifting the business focus toward halal activities that align with Islamic principles.

3. **Evaluate the Partnership**: If the business partner insists on moving forward with the unethical venture despite the objections, the Muslim partner may need to reconsider their involvement. Continuing to be part of a business venture that involves haram practices would compromise their religious integrity. In such a case, the Muslim should assess whether they can legally exit the partnership, negotiate a buyout, or dissolve the business arrangement.

4. **Seek Islamic Guidance**: If unsure about the best course of action, the Muslim partner can consult with a knowledgeable Islamic scholar or a trusted local imam for specific advice tailored to their situation. Islamic financial advisory services or boards specializing in halal business practices may also offer valuable insights.

5. **Protecting Religious Integrity**: If leaving the partnership or withdrawing from the business venture is not immediately feasible, the Muslim partner should consider limiting their involvement in the haram aspects of the business as much as possible. This could mean distancing themselves from the interest-earning or gambling-related components, if applicable, and making sure that their personal actions do not indirectly support such practices.

6. **Trust in Allah’s Support**: Maintaining the focus on one’s faith and trusting in Allah’s reward for making decisions that uphold Islamic values is crucial. Islam teaches that taking a stand for what is right, even at a personal cost, will lead to divine support and reward.

Ultimately, the Muslim partner must prioritize their faith and religious obligations, even if it requires difficult decisions or changes in the business arrangement. It is better to sacrifice worldly profit than to jeopardize one’s religious integrity.