This excerpt from the Baudhayana Shrauta Sutras, a text associated with the Yajur Veda, describes a ritual which ironically is not from the Yajur Veda:
athātathchandasyanāmrātāni hutānumantraṇāni vyākhyāsyāmaḥ।vaimṛdha– miṣṭamanumantrayata indrasya vaimṛdhasyāhaṃ devayajyayendriyāvyasapatno vīryavāñchīmānbhūyāsamityasapatno vīryavānbhūyāsamiti vā । parjanyasyāhaṃ devayajyayā suyavaso bhūyāsam । somasyāhaṃ devayajyayā pra prajayā ca paśubhiśca janiṣīya suretā reto dhiṣīyeti vā । saviturahaṃ devayajyayā svastimānpaśumānbhūyāsam। sarasvatyā ahaṃ devayajyayā vācamannādya puṣeyam । sarasvato 'haṃ devayajyayā śraddhāmanā bhūyāsam । pūṣṇo 'haṃ devayajyayā puṣṭimānpaśumānbhūyāsam । marutāmahaṃ devayajyayā prāṇairṛdhyāsam। viśveṣāṃ devānāmahaṃ devayajyayā prāṇaiḥ sāyujyaṃ gameyam । dyāvāpṛthivyorahaṃ devayajyayobhayolakiyoṛdhyāsaṃ bhūmānaṃ pratiṣṭhāṃ gameyamitivā। vājināmahaṃ devayajyayā retasvī bhūyāsam । varuṇasyāhaṃ devayajyayā dharmabhāgbhūyāsam । kasyāhaṃ devayajyayā śaviṭho bhūyāsam। viśvakarmaṇo 'haṃ devayajyayā viśvāni karmāṇyavarundhīya । adityā ahaṃ devayajyayāśhaso mucyeya । vāyorahaṃ devayajyayā ratnabhāgbhūyāsam। sūryasyāhaṃ devayajyayā sudṛśīko bhūyāsam। agrāviṣṇavorahaṃ devayajyayā vīryavānbhūyāsam। viṣṇoraha
Now we shall explain the followings of offerings (by the sacrificer) not recorded in the (Taittiriya) Veda. He follows the offering to Vaimrdha Indra with the formula, "May I become powerful, without an enemy, possessing valour and wealth through the offering to Vaimrdha Indra" or "... without an enemy and possessing valour." "May I become possessing ample barley through the offering to Parjanya." "May I propagate offspring and cattle through the offering to Soma," or "May I have seminal fluid and be possessing ample seminal fluid." "May I befaring well and possessing cattle through the offering to Savitr." "May I develop power of speech and food through the offering to Sarasvati." "May I become faithful-minded through the offering to Sarasvant." "May I become prosperous and possessing cattle through the offering to Pusan." "May I become accomplished with vital breaths through the offering to Maruts." "May I be associated with vital breaths through the offering to Visve Devas." "May I prosper in both the worlds through the offering to Dyavaprthivi," or "May I obtain abundance and stability." "May I be possessing seminal fluid through the offering to Vajins." "May I be observing law through the offering to Varuna." "May I become mighty through the offering to Ka." "May I achieve all deeds through the offering to Visvakarman." "May I be relieved of evil through the offering to Aditi." "May I be receiving gifts through the offering to Vayu." "May I be possessing good sight through the offering to Surya." "May I become possessing valour through the offering to Agni-Visnu," "May I become pervaded by rays throgh the offering to Visnu." "May I reach the heaven through the offering to Aryaman." In this way he follows the offering to the relevant divinity.
Now most of these gods are recognizable: you have Indra king of the gods, Parjanya the rain god, Chandra the moon god, Surya the sun god, Saraswati goddess of learning, Sarasvant the mysterious male counterpart to Saraswati (whom I may post a question about in future), Pushan god of cattle, the Maruts or storm gods, the Vishve Devas or all-gods, Dvayaprithvi or the gods of heaven and earth, Varuna the ocean god, Brahma god of creation, the divine architect Vishwakarma, Aditi mother of the gods, Vayu the wind god, Agni the fire god, Vishnu god of preservation, and Aryaman god of departed ancestors.
But I'm interested in the part in bold. My question is, who are the Vajin gods mentioned in the passage?
If it helps, the Sanskrit word "vajin" means horse. It's possible that they're connected to the Rashmi gods I asked about in my question here, who are also described in the Baudhayana Shrauta Sutras. The reason I say they may be connected is that the Sanskrit word "rashmi" means reins of a horse.