Here are the two verses in question from Rigveda Book 1 Hymn 163
यदक्रन्दः परथमं जायमान उद्यन समुद्रादुत वा पुरीषात |
शयेनस्य पक्षा हरिणस्य बाहू उपस्तुत्यं महि जातं ते अर्वन ||
Here's the translation from Ralph Griffith :
WHAT time, first springing into life, thou neighedst, proceeding from the sea or upper waters, Limbs of the deer hadst thou, and eagle pinions. O Steed, thy birth is nigh and must be lauded.
The entire hymn is titled 'The Horse'. I want to understand why is this horse (arvan) said to arise from the sea ? What's the context of this praise of the horse ?