Why Does Meditative Concentration Bring the Merit of Concentration (Samādhi)?

Question: Why does meditative concentration (samādhi) bring the merit of concentration? 

Answer: Meditative concentration is divided into the concentration of the desire realm, the concentration of the form realm, and the concentration of the formless realm. When the mind's discrimination corresponds to the states of the desire-realm heavens, the form-realm heavens, and the formless-realm heavens, then after death one will be reborn in the desire realm, the form realm, or the formless realm, becoming a heavenly being, enjoying the superb retributive rewards of the heavenly realms, abiding in the corresponding meditative concentration and experiencing bliss. Therefore concentration has the merit of concentration. The merit of concentration is worldly merit—the merit enjoyed within the world, the merit enjoyed within the world of the three realms. Concentration represents purity, and purity is merit. Many people wish to be pure but cannot attain purity, which shows they lack the merit of purity. Concentration can make the body and mind comfortable and at ease, so concentration has the merit of concentration. Concentration can subdue and eliminate afflictions; without afflictions, the mind gains liberation, so concentration has the merit of concentration. Concentration can give rise to wisdom, so concentration has the merit of concentration. Concentration can expel scattered thoughts and trivial matters, remove interference, and allow one to enjoy a splendid time of pure happiness, so concentration has the merit of concentration. Concentration can give rise to immeasurable supernormal powers and spiritual capabilities, can initiate vast and superb practices, can benefit oneself and benefit others, can accomplish all worldly and world-transcending endeavors, and can accomplish all worldly and world-transcending wisdom; therefore concentration has the merit of concentration. 

Concentration can avert disasters. For example, in the fourth dhyāna, where one abandons thought and attains purity, the three calamities cannot reach it; therefore concentration has the merit of concentration. As long as there are thoughts in the mind, disasters can be attracted. Great karmic activity, especially karmic activity accompanied by afflictions, brings even more disasters. When the mind is pure, discarding thoughts and desires, without craving or seeking, one will not attract disasters. However, the fourth dhyāna is not ultimate either. After the meditative concentration fades away, feelings of suffering will appear. Every kind of meditative concentration is subject to arising and ceasing; without realizing the fruits, without awakening to the true mind, and without cultivating to a considerably high level of wisdom, meditative concentration will eventually fade away, and after it fades, afflictions and disasters will appear. The merit of concentration that is not grounded in seeing the truth is tainted (sāsrava) merit; once the merit is exhausted, it will vanish completely. Therefore one should still pursue the liberating wisdom born from meditative concentration—this is the superb retributive reward that endures forever.