Is the decline in religious and worldly commitment after experiencing fraud in a business venture considered 'ayn (evil eye) or hasad (envy), and what is the cure for such a state?

What has befallen you is not envy (hasad) or evil eye (ayn), but rather the effect of associating with that man and his partnership in the project. Indeed, one's companion has a great impact on their happiness or misery, as indicated by the noble verses of the Quran and the prophetic hadiths.

Therefore, we advise you, first, to separate from him, and then to begin strengthening your faith and gaining God's love by following ten reasons, which include: contemplating the Quran, drawing closer to God through supererogatory acts of worship (nawafil), constant remembrance (dhikr), preferring what God loves, contemplating His names and attributes, observing His benevolence and kindness, the breaking of the heart before Him, being alone with Him during the divine descent (nuzool ilahi), avoiding everything that hinders the heart from God, and associating with sincere lovers (of God).