SHANTAKARAM BHUJANGASHAYANAM PADMANABHAM SURESHAM,
VISHWADHARAM GAGAN SADRISHAM MEGHAVARNAM SHUBHANGAM |
LAKSHMIKANTAN KAMALNAYANAM YOGIMIRDHYANA GAMYAM,
VANDE VISHNUM BHAVA BHAYAHARAM SARVA LOKAIKNATHAM ||
I worship that Lord Vishnu who has a peaceful body
(postures); who rests on Sheshanaga (the mighty serpant - cobra); who
has a lotus in his navel, who is the base of the world, who is like
the sky; who has a colour like cloud, who is the lord of Lakshmi
(wealth); who has eyes like lotus; who is seen by yogis in their
meditation; who is the remover of all the differences and who is the
only Lord of all the three Lokas (Worlds), I worship such Lord Vishnu.
Vishnu rests on Sheshnag because it symbolizes that one who has reached the Ultimate Enlightenment, should be in peace and without tension or stress of mind, knowing that Sheshnag, a snake (allegorical to materialistic troubles) is hovering above him.
So one who wants peace, must worship Vishnu.
Why does Lord Vishnu rest on Sheshnag?
Brahma Purana:
The second virtue (resting on the Sheshanaga) must be considered as
the sub-virtue of the peaceful appearance. Scriptures describe
Sheshanaga as Kala also. Sheshanaga is a highly
poisonous snake. But Lord Vishnu rests on him without fear or
worries. One should not to lose patience even while facing the kala
itself; instead strive to ride on it, only then can one
remain in peaceful appearance. If the fear overpowers, it may
shatter peace. The worshipers who want salvation should be peaceful.
Why does Vishnu rest on a Sagar (Ksheerodak, Garbhodak or Karanodak). Chanakyaneeti explains it thus.
KA CHINTA MAM JIVANE YADI HARIIVISHVAMMBHARO GEEYATE,
NO CHEDARBHAKA JIVANAY JANANISTANYAM KATHM NIRMYET |
ITYALOCHYMUHURMUHURYADUPATE LAKSHMIPATE KEWAL
TVATPADAMSHUJASEVANEN SATATAM KALOMAYA NEEYATE ||
If God Hari Vishnu is known as VISHVAMBHAR (feeder of the
world) I need not worry for anything in the world. If he were not
there, where the milk would come from in the breast of a mother before
child's birth. So God filled the breast of a new mother with complete
food that is milk.