The number 7 has a significance important to the seers of the Rig Veda.
Rig Veda mentions:
Sapta Rishis (Seven ages; also in the sky as Ursa Major constellation)
Sapta Sindhu (Seven Rivers in Punjab)
Seven horses of sun
Seven mouths of Brihaspati
Seven priests at the sacrifice
Seven holy places
Seven castles of the aerial demons destroyed by indra
Seven holy singers
Seven rays of sun
Seven tongues/ flames of Agni (Fire)
Seven male children
Seven elements
Seven Adityas
Seven foundations of the sea
Seven races of men
Seven heads, 7 hands, 7 tongues
Seven threads
Seven germs within the seed
Seven meters
Seven tones
Sapta Vadhri
(This list is taken from The Rig Veda – A Historical Analysis by Shrikant G Talageri)
Refer here
Sanskrit text [Accents, Plain, Transliterated]: सोमा॑रुद्रा
धा॒रये॑थामसु॒र्यं१॒॑ प्र वा॑मि॒ष्टयोऽर॑मश्नुवन्तु । दमे॑दमे स॒प्त
रत्ना॒ दधा॑ना॒ शं नो॑ भूतं द्वि॒पदे॒ शं चतु॑ष्पदे ॥ सोमारुद्रा
धारयेथामसुर्यं प्र वामिष्टयोऽरमश्नुवन्तु । दमेदमे सप्त रत्ना दधाना शं
नो भूतं द्विपदे शं चतुष्पदे ॥ somārudrā dhārayethām asuryam pra vām
iṣṭayo 'ram aśnuvantu | dame-dame sapta ratnā dadhānā śaṃ no bhūtaṃ
dvipade śaṃ catuṣpade ||
English translation: “Soma and Rudra, confirm (in us the strength) of
asuras may sacrifices in every dwelling adequately reach you; do you,
possessors of the seven precious things, bestow happiness upon us;
happiness upon our bipeds and quadrupeds.”
Let us refer to Sāyaṇa's Ṛgveda-bhāṣya
Possessors of seven precious things: sapta ratnā dadhāna; perhaps a
reference to seven dhātus or seven elements
Refer to the Seven dhātus here
