सुबाहु: श्रुतसेनश्च शत्रुघ्नस्य बभूवतु: । गन्धर्वान् कोटिशो जघ्ने भरतो विजये दिशाम् ॥ १३ ॥ तदीयं धनमानीय सर्वं राज्ञे न्यवेदयत् । शत्रुघ्नश्च मधो: पुत्रं लवणं नाम राक्षसम् । हत्वा मधुवने चक्रे मथुरां नाम वै पुरीम् ॥ १४ ॥
subāhuḥ śrutasenaś ca śatrughnasya babhūvatuḥ gandharvān koṭiśo jaghne bharato vijaye diśām
Śatrughna had two sons, Subāhu and Śrutasena. During Bharata’s conquest of the directions, he slew many millions of Gandharvas and brought their wealth to offer it all to King Rāmacandra. Śatrughna also killed the rākṣasa Lavaṇa, son of Madhu, and thus founded the city called Mathurā within the great forest of Madhuvana.
In Canto 9, Chapter 11, Śukadeva states that Śatrughna killed the rākṣasa Lavaṇa (son of Madhu) and then established a city in the Madhu forest named Mathurā.
The verse shows Bharata acting in kṣatriya-dharma and loyalty to the throne—after victory he offered all acquired wealth to the reigning king (Lord Rāma), demonstrating service and proper royal conduct.
Use power and success in the service of dharma: protect society from harmful forces, and dedicate gains back to rightful duty and leadership rather than personal enjoyment.