Srimad-Bhagavatam: Canto 4 - Chapter 1 - Verse 45

Sanskrit:

मैत्रेय उवाचइति ब्रुवाणं नृपतिं पितृदेवद्विजातय: ।तुष्टुवुर्हृष्टमनस: साधुवादेन साधव: ॥ ४५ ॥

ITRANS:

maitreya uvācaiti bruvāṇaṁ nṛpatiṁpitṛ-deva-dvijātayaḥtuṣṭuvur hṛṣṭa-manasaḥsādhu-vādena sādhavaḥ

Translation:

The great sage Maitreya said: After hearing King Pṛthu speak so nicely, all the demigods, the denizens of Pitṛloka, the brāhmaṇas and the saintly persons present at the meeting congratulated him by expressing their good will.

Purport:

When a person speaks very nicely at a meeting, he is congratulated by the audience, who express their good will with the words sādhu, sādhu. This is called sādhu-vāda. All the saintly persons, Pitās (denizens of Pitṛloka) and demigods who were present at the meeting and heard Pṛthu Mahārāja expressed their good will with the words sādhu, sādhu. They all accepted the good mission of Pṛthu Mahārāja, and they were fully satisfied.