لَا رَيْبَ فِيهِ
- لَا negates the whole class.
- رَيْبَ is its ism, built on fathah in the position of nasb, without tanwin.
- فِيهِ completes the statement as the khabar.
Do not read رَيْبَ as the marfu ism pattern رَجُلٌ from لَا رَجُلٌ صَالِحًا. The two uses of لَا are different.