What is the ruling on participating with a farmer who bought equipment through the bank and has not yet paid its price? Is the money earned from it unlawful? And is it out of piety not to participate with him?

A farmer's purchase of his tools with an interest-based loan does not prevent you from partnering with him or dealing with him, because the prohibition of the loan relates to his own responsibility, not to the tools themselves. However, if you seek piety and caution, do not partner with him; as some scholars disliked partnering with those who do not avoid the unlawful, fearing that the unlawful might affect their partner.