According to the Gaudiya Vaishnava tradition, gopi-chandana, or the sacred mud from Dwaraka, is applied on the body in twelve places while reciting mantras to Lord Vishnu. This process purifies one's body, designating it as a temple of the Lord. Besides purification, the tilak also offers the wearer protection from ghosts, evil influences, bad dreams, accidents and many other things. It keeps one's mind calm and allows one to constantly remember Lord Krishna. 

The following story from the Garga Samhita describes the wonderful glories of the sacred mud known as gopi-chandana. 

[From Garga Samhita, Canto Six, Chapter Fifteen, Translation by Sri Kushakratha Das]  

Text 15

yasya sravana-matrena
karma-bandhat pramucyate
gopinam yatra vaso 'bhut
tena gopi-bhuvah smrtah 

Simply by hearing about Gopi-bhumi, which is so named because the gopis resided there, one become free from the bondage of karma. 

Text 16 

gopy-angaraga-sambhutam
gopi-chandanam uttamam
gopi-chandana-liptango
ganga-snana-phalam labhet 

In Gopi-bhumi gopi-chandana was manifested from the gopis' cosmetics. A person who marks his limbs with gopi-chandana tilaka attains the result of bathing in the Ganga. 

Text 17 

maha-nadinam snanasya
punyam tasya dine dine
ngopi-chandana-mudrabhir
mudrito yah sada bhavet 

A person who daily wears gopi-chandana tilaka attains the pious result of daily bathing in all sacred rivers. 

Text 18 

asvamedha-sahasrani
rajasuya-satani ca
sarvani tirtha-danani
vratani ca tathaiva ca
krtani tena nityam vai
sa krtartho na samsayah 

A person who daily wears gopi-chandana tilaka attains the result of performing a thousand asvamedha-yajnas and a hundred rajasuya-yajnas. He attains the reusult of giving charity and following vows at all holy places. He attains the goal of life. Of this there is no doubt. 

Text 19 

ganga-mrd-dvi-gunam punyam
citrakuta-rajah smrtam
tasmad dasa-gunam punyam
rajah pancavati-bhavam 

Twice as sacred as the mud of the Ganga is the dust of Chitrakuta. Ten times more sacred than that is the dust of Panchavati-tirtha. 

Text 20 

tasmac chata-gunam punyam
gopi-chandanakam rajah
gopi-chandanakam viddhi
vrndavana-rajah-samam 

A hundred times more sacred is the dust of gopi-chandana. Please know that gopi-chandana is equal to the dust of Vrindavana. 

Text 21

gopi-chandana-liptangam
yadi papa-satair yutam
tam netum na yamah sakto
yama-dutah kutah punah

Even if in the past he has committed hundreds of sins, if a person wears gopi-chandana tilaka, then Yamaraja cannot take him away. How, then, can Yamaraja's messengers touch him? 

Text 22

nityam karoti yah papi
gopi-chandana-dharanam
sa prayati harer dhama
golokam prakrteh param  

A sinner who daily wears gopi-chandana tilaka goes to Lord Krishna supreme abode, Goloka, which is beyond the world of matter. 

Text 23 

sindhu-desasya rajabhud
dirghabahur iti srutah
anyaya-varti dustatma
vesya-sanga-ratah sada 

In Sindhu-desa there was a king named Dirghabahu. He was cruel and sinful and he was addicted to visiting prostitutes.

Text 24 

tena vai bharate varse
brahma-hatya-satam krtam
dasa garbhavati-hatyah
krtas tena duratmana 

While he was on the earth this cruel sinner murdered a hundred brahmanas and ten pregnant women.

Text 25 

mrigayayam tu banaughaih
kapila-go-vadhah krtah
saindhavam hayam aruhya
mrgayarthi gato 'bhavat 

One day he mounted a sindhu horse and went hunting. With a flood of arrows he accidentally killed with a brown cow in that hunt. 

Text 26 

ekada rajya-lobhena
mantri kruddho maha-khalam
jaghanaranya-dese tam
tiksna-dharena casina  

One day, greedy to get his kingdom, with a sharp sword his angry minister killed him in the forest. 

Text 27 

bhu-tale patitam mrtyu-
gatam viksya yamanugah
baddhva yama-purim ninyur
harsayantah parasparam 

Seeing him fallen to the ground and dead, the Yamadutas came, bound him, and, joking as they went, took him to the city of Yamaraja.

Text 28 

sammukhe 'vasthitam viksya
papinam yama-rad bali
citraguptam praha turnam
ka yogya yanatasya vai 

Seeing this sinner brought before him, powerful Yamaraja said to his scribe Chitragupta, "What is the proper punishment for him?" 

Text 29

sri-chitragupta uvaca

catur-asiti-laksesu
narakesu nipatyatam
nihsandeham maha-raja
yavac candra-divakarau 

Sri Chitragupta said: O great king, he should be thrown into eight million four hundred thousand hells for as long as the sun and the moon shine in the sky. 

Text 30

  anena bharate varse
ksanam na su-krtam krtam
dasa-garbhavati-ghatah
kapila-go-vadhah krtah 

On the earth he did not perform a single pious deed. He killed ten pregnant women. He killed a brown cow.

Text 31

tatha vana-mriganam ca
krtva hatyah sahasrasah
tasmad ayam maha-papi
devata-dvija-nindakah 

He killed thousands of deer in the forest. He offended the demigods and the brahmanas. He is a great sinner. 

Texts 32 and 33

sri-narada uvaca
tada yamajnaya duta
nitva tam papa-rupinam
sahasra-yojanayame
tapta-taile maha-khale

sphurad aty-ucchalat-phene
kumbhipake nyapatayan
pralayagni-samo vahnih
sadyah sitalatam gatah

Sri Narada said: Then, by Yamaraja's order, the Yamadutas took that sinner and threw him into a terrible, eight-thousand mile wide cauldron of bubbling boiling oil in the hell of Kumbhipaka. The moment that sinner came to it, the boiling oil, which was as hot as the great fires at the time of cosmic devastation, suddenly became cool. 

Text 34

vaideha tan-nipatanat
prahlada-ksepanad yatha
tadaiva citram acakhyur
yama-duta mahatmane 

O king of Videha, as Prahlada was unhurt in the same situation, that sinner was not hurt by the boiling oil. Then the Yamadutas described that great wonder to noble-hearted Yamaraja. 

Text 35 

anena su-krtam bhumau
ksanavan na krtam kvacit
citraguptena satatam
dharma-rajo vyacintayat 

Yamaraja and Chitragupta carefully reviewed the sinner's case and concluded that while he was on the earth the sinner had not for a moment performed even a single pious deed. 

Text 36 

sabhayam agatam vyasam
sampujya vidhivan nrpa
natva papraccha dharmatma
dharma-rajo maha-matih 

Then Vyasadeva arrived in that assembly. Bowing down before Him, and carefully worshiping Him, saintly and noble-hearted Yamaraja asked Vyasadeva the following question. 

Text 37  

sri-yama uvaca

anena papina purvam
na krtam su-krtam kvacit
sphurad-agny-ucchalat-phene
kumbhipake maha-khale  

asya ksepanato vahnih
sadyah sitalatam gatah
iti sandehatas cetah
khidyate me na samsayah  

Sri Yamaraja said: When a certain sinner, who had never performed even a single pious deed, was thrown into the terrible boiling oil of Kumbhipaka, the oil suddenly became cool. Because of this my mind is now tortured with doubts. 

Text 39 

sri-vyasa uvaca

suksma gatir maha-raja
vidita papa-punyayoh
tatha brahma-gatih prajnaih
sarva-sastra-vidam varaih 

Sri Vyasadeva said: O great king, the intelligent sages, who have studied all the scriptures, know that the ways of piety, sin, and spiritual progress are very subtle and difficult to understand. 

Text 40 

daiva-yogad asya punyam
praptam vai svayam arthavat
yena punyena suddho 'sau
tac chrnu tvam maha-mate 

Somehow or other, by destiny, this sinner did perform a pious deed, and by that deed he became purified. O noble-hearted one, please hear the story of this. 

Text 41 

kasyapi hastato yatra
patita dvaraka-mrdah
tatraivayam mrtah papi
suddho 'bhut tat-prabhavatah 

That sinner died in a place where from someone's hand some gopi-chandana from Dvaraka had accidentally fallen. Dying in gopi-chandana, that sinner became purified.  

Text 42 

gopi-chandana-liptango
naro narayano bhavet
etasya darsanat sadyo
brahma-hatya pramucyate 

A person who wears gopi-chandana tilaka attains a spiritual form like that of Lord Narayana. Simply by seeing him one becomes free of the sin of killing a brahmana.  

Texts 43 and 44

sri-narada uvaca

iti srutva dharma-rajas
tam aniya visesatah
vimane kama-ge sthapya
vaikuntham prakrteh param

 presayam asa sahasa
gopi-chandana-kirti-vit
evam te kathitam rajan
gopi-chandanakam yasah  

Sri Narada said: Hearing this, Yamaraja, who understands the glories of gopi-chandana, took the sinner, placed him a an airplane that goes anywhere one wishes, and sent him to Vaikuntha, which is above the worlds of matter. O king, thus I have described to you the glories of gopi-chandana. 

Text 45 

gopi-chandana-mahatmyam
yah srnoti narottamah
sa yati paramam dhama
sri-krishnasya mahatmanah 

One who hears this account of gopi-chandana's glories becomes exalted. He goes to the supreme abode of Lord Krishna, the Supreme Personality of Godhead.