Valmiki Ramayana Sundara Kanda Sarga 56 Shloka 23
Original Shlokaस तमारुह्य शैलेन्द्रं व्यवर्धत महाकपिः। दक्षिणादुत्तरं पारं प्रार्थयन् लवणाम्भसः।।5.56.23।।
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सः महाकपिः that great Hanuman, लवणाम्भसः of the saltwater ocean, दक्षिणात् from the South, उत्तरं पारम् towards northern shore, प्रार्थयन् desiring, तं शैलेन्द्रम् that king of mountains, आरुह्य having ascended, व्यवर्धत started enlarging body.
On ascending the king of mountains, desiring to reach the northern shore of the saltwater ocean from the Southern shore, he enlarged his body (in preparation to leap).