Rig Veda 1.25.8

Sanskrit text [Accents, Plain, Transliterated]:

वेद॑ मा॒सो धृ॒तव्र॑तो॒ द्वाद॑श प्र॒जाव॑तः । वेदा॒ य उ॑प॒जाय॑ते ॥
वेद मासो धृतव्रतो द्वादश प्रजावतः । वेदा य उपजायते ॥
veda māso dhṛtavrato dvādaśa prajāvataḥ | vedā ya upajāyate ||

English translation:

“He, who accepting the rites (dedicated to him) knows the twelve months and their productions and that which is supplementarily engendered.”

Commentary by Sāyaṇa: Ṛgveda-bhāṣya

An allusion to the thirteenth, the supplementary or intercalary month of the Hindu unisolar year and to the transition to the lunar year from the solar year; 'that thirteenth or additional month which is produced of itself, in connection with the year', yaḥ trayodaśo adhikamāsa upajāyate saṃvatsarasamīpe svayam evotpadyate

Details:

Ṛṣi (sage/seer): śunaḥśepa ājīgartiḥ [śunaśepa ājīgarti];
Devatā (deity/subject-matter): varuṇaḥ;
Chandas (meter): nicṛdgāyatrī ;
Svara (tone/note): Swar;

Padapatha [Accents, Plain, Transliterated]:

वेद॑ । मा॒सः । धृ॒तऽव्र॑तः । द्वाद॑श । प्र॒जाऽव॑तः । वेद॑ । यः । उ॒प॒ऽजाय॑ते ॥
वेद । मासः । धृतव्रतः । द्वादश । प्रजावतः । वेद । यः । उपजायते ॥
veda | māsaḥ | dhṛta-vrataḥ | dvādaśa | prajāvataḥ | veda | yaḥ | upa-jāyate

Multi-layer Annotation of the Ṛgveda

[Rigveda 1.25.8 English analysis of grammar]