Srimad-Bhagavatam: Canto 10 - Chapter 1 - Verse 23-26

Sanskrit:

भीष्मो द्रोणोऽम्बिकापुत्रो गान्धारी ससुता तथा ।सदारा: पाण्डवा: कुन्ती सञ्जयो विदुर: कृप: ॥ २३ ॥कुन्तीभोजो विराटश्च भीष्मको नग्नजिन्महान् ।पुरुजिद्‌द्रुपद: शल्यो धृष्टकेतु: सकाशिराट् ॥ २४ ॥दमघोषो विशालाक्षो मैथिलो मद्रकेकयौ ।युधामन्यु: सुशर्मा च ससुता बाह्लिकादय: ॥ २५ ॥राजानो ये च राजेन्द्र युधिष्ठिरमनुव्रता: ।श्रीनिकेतं वपु: शौरे: सस्‍त्रीकं वीक्ष्य विस्मिता: ॥ २६ ॥

ITRANS:

bhīṣmo droṇo ’mbikā-putrogāndhārī sa-sutā tathāsa-dārāḥ pāṇḍavāḥ kuntīsañjayo viduraḥ kṛpaḥ

Translation:

All the royalty present, including Bhīṣma, Droṇa, Dhṛtarāṣṭra, Gāndhārī and her sons, the Pāṇḍavas and their wives, Kuntī, Sañjaya, Vidura, Kṛpācārya, Kuntībhoja, Virāṭa, Bhīṣmaka, the great Nagnajit, Purujit, Drupada, Śalya, Dhṛṣṭaketu, Kāśirāja, Damaghoṣa, Viśālākṣa, Maithila, Madra, Kekaya, Yudhāmanyu, Suśarmā, Bāhlika with his associates and their sons, and the many other kings subservient to Mahārāja Yudhiṣṭhira — all of them, O best of kings, were simply amazed to see the transcendental form of Lord Kṛṣṇa, the abode of all opulence and beauty, standing before them with His consorts.

Purport:

According to Śrīla Śrīdhara Svāmī, all these kings were now followers of Yudhiṣṭhira because he had subjugated each of them to earn the privilege of performing the Rājasūya sacrifice. The Vedic injunctions state that a kṣatriya who wants to execute the Rājasūya for elevation to heaven must first send out a “victory horse” to roam freely; any other king whose territory this horse enters must either voluntarily submit or face the kṣatriya or his representatives in battle.