What is the ruling on a man saying to someone who embraced Islam out of desire for Paradise: "Your faith is weak and commercial," and his saying about the reason for his conversion: "I believed in Allah because I found no one else worthy of worship, and if I had, I would have believed in them"?

The believer worships Allah because He is worthy of worship, out of hope for His mercy and Paradise, and out of fear of His punishment and Hellfire. There is no contradiction in this; rather, it is the correct approach, as Allah Almighty says about the prophets: "Indeed, they used to hasten to good deeds and supplicate Us with hope and fear, and they were to Us humbly submissive."