Why do we observe special rituals during the time of an eclipse?
In slok 86 and slok 87 of the Shikshapatri, Lord Swaminarayan has commanded His disciples to stop all other activities, purify themselves and chant the Swaminarayan mantra during a solar or lunar eclipse. When the eclipse is over, they should bathe fully clothed (so that the clothes are also washed and purified) and then gruhastha disciples should give charitable donations according to their means, and tyagis should perform pooja.
The Puran (scriptures) narrate the story behind the conception of eclipses. After the Samudramanthan period, the time when the oceans were dramatically churned, the deities (good) and the deityas (evil) fought over the miraculous pot of nectar. The deityas managed to take possession of the nectar and fled.
Lord Vishnu realised that if deityas consumed the nectar, they would become more powerful than the deities and they would terrorise the entire world. Therefore, he assumed the enchanting form of Mohini. The beauty of Mohini was so great that she had previously infatuated even the strictly austere Lord Shiv.
Mohini managed to infatuate the deityas and brought the deities and the deityas together. She grabbed hold of the pot of nectar and asked everyone to sit in two lines, facing each other, so that she could serve them all with the nectar. All the deities sat in one line and the deityas sat in another. Mohini started serving the deities. It was her plan that the nectar would be finished by the time she got to the deityas. However, the deitya called Ketu realised what she was doing. Ketu disguised himself as a deity and sat in between Surya (the sun deity) and Chandra (the moon deity).
Mohini poured the nectar into Surya's mouth and then proceeded to give the nectar to Ketu. At that moment, the Surya and Chandra deities realised that this was an impostor and started to shout. Immediately, Mohini grabbed her sword and cut off Ketu's head. However, the magical nectar had already entered Ketu's body. Half of the nectar was in his body, whilst the other half remained in his mouth. As nectar had come into contact with both parts, they both became immortal and assumed individual forms. The head portion is known as Rahu, and the body portion is known as Ketu.
As it was the Surya and Chandra deities who revealed Ketu's identity to Mohini, Rahu vowed to take his revenge on them. They are constantly engaged in battle and so periodically, Rahu will swallow the moon or the sun. However, as Rahu has no body, they manage to escape through Rahu's open neck region. The time period that Rahu swallows the deities, is the time of an eclipse. As the Sun and Moon are both so essential for all life, disciples of the Lord must pray whenever they have to endure such distress, in the same manner as one prays to God whenever a close relative or friend is ill.
During this these times, various duties need to be observed. Several hours before the start of an eclipse, one must commence a fast. Everyone is inflicted by sutak (period of ritual impurity) at the sight of Rahu. Therefore, from the start of an eclipse, i.e. from when Rahu becomes visible, anything that one touches also becomes impure and must be washed at the end of the eclipse. Any cooked food becomes impure. It should all be discarded before the start of an eclipse. Generally, the entire house is cleaned in preparation for an eclipse.
The rituals of an eclipse only need to be observed in the regions that it will be visible.
Anyone who does not observe the eclipse rituals and do not bathe at the end of an eclipse, are considered Sutaki (ritually impure) until the time of the next eclipse.
Lord Swaminarayan has endorsed that His disciples must observe these restrictions. Just as the time of a birth or death within a family are regarded as being ritually impure periods, the time of an eclipse is also considered in the same manner.