SB 5.24.3
tan nisamyobhayatrapi bhagavata raksanaya prayuktam sudarsanam nama bhagavatam dayitam astram tat tejasa durvisaham muhuh parivartamanam abhyavasthito muhurtam udvijamanas cakita-hrdaya arad eva nivartate tad uparagam iti vadanti lokah.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
After hearing from the sun and moon demigods about Rahu’s attack, the Supreme Personality of Godhead, Visnu, engages His disc, known as the Sudarsana cakra, to protect them. The Sudarsana cakra is the Lord’s most beloved devotee and is favored by the Lord. The intense heat of its effulgence, meant for killing non-Vaisnavas, is unbearable to Rahu, and he therefore flees in fear of it. During the time Rahu disturbs the sun or moon, there occurs what people commonly know as an eclipse.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The Supreme Personality of Godhead, Visnu, is always the protector of His devotees, who are also known as demigods. The controlling demigods are most obedient to Lord Visnu, although they also want material sense enjoyment, and that is why they are called demigods, or almost godly. Although Rahu attempts to attack both the sun and the moon, they are protected by Lord Visnu. Being very afraid of Lord Visnu’s cakra, Rahu cannot stay in front of the sun or moon for more than a muhurta (forty-eight minutes). The phenomenon that occurs when Rahu blocks the light of the sun or moon is called an eclipse. The attempt of the scientists of this earth to go to the moon is as demoniac as Rahu’s attack. Of course. their attempts will be failures because no one can enter the moon or sun so easily. Like the attack of Rahu, such attempts will certainly be failures.