There are three vows in all:

1. paritranaya sadhunam

vinasaya ca duskrtam

dharma-samsthapanarthaya
sambhavami yuge yuge

(Bhagavad Gita 4:8)

"For the protection of the good and the punishment of the bad, for the establishment of the Moral Order, I shall concretise Myself, age after age".

2. ananyas cintayanto mam

ye janah paryupasate

tesam nityabhiyuktanam

yoga-ksemam vahamy aham

(Bhagavad Gita 9:22)

"Whoever is wholly immersed in My contemplation, with no other thought, I shall be ever with Him- and I shall bear the burden of his welfare".

3. sarva-dharman parityajya

mam ekam sharanam vraja

aham tvam sarva-papebhyo

mokshayishyami ma shuchah

(Bhagavad Gita 18:66)

"Surrender unto Me, giving up all other duties and obligations; I shall liberate you from all sin; do not grieve."

These are the three vows that Krishna has taken, and the armlets are reminders of these tasks on which He is set.