One verse

Srimad Bhagavatam 5.20.44

5.20.44

मृतेऽण्ड एष एतस्मिन् यदभूत्ततो मार्तण्ड इति व्यपदेश: । हिरण्यगर्भ इति यद्धिरण्याण्डसमुद्भ‍व: ॥ ४४ ॥

mrte ’nda esa etasmin yad abhut tato martanda iti vyapadesah; hiranyagarbha iti yad dhiranyanda-samudbhavah.

mrte
dead
ande
in the globe
esah
this
etasmin
in this
yat
which
abhut
entered personally at the time of creation
tatah
from that
martanda
Martanda
iti
thus
vyapadesah
the designation
hiranya-garbhah
known as Hiranyagarbha
iti
thus
yat
because
hiranya-anda-samudbhavah
his material body was created from Hiranyagarbha.

The sun-god is also known as Vairaja, the total material body for all living entities. Because he entered this dull egg of the universe at the time of creation, he is also called Martanda. He is also known as Hiranyagarbha because he received his material body from Hiranyagarbha (Lord Brahma).