Verse 2.15.2

स य एवमेतद्वैरूपं पर्जन्ये प्रोतं वेद विरूपांश्च सुरूपंश्च पशूनवरुन्धे सर्वमायुरेति ज्योग्जीवति महान्प्रजया पशुभिर्भवति महान्कीर्त्या वर्षन्तं न निन्देत्तद्व्रतम् ॥ २.१५.२ ॥
॥ इति पञ्चदशः खण्डः ॥

sa ya evametadvairūpaṃ parjanye protaṃ veda virūpāṃśca surūpaṃśca paśūnavarundhe sarvamāyureti jyogjīvati mahānprajayā paśubhirbhavati mahānkīrtyā varṣantaṃ na nindettadvratam || 2.15.2 ||
|| iti pañcadaśaḥ khaṇḍaḥ ||

2. He who knows that this Sāma called Vairūpa has its source in the clouds comes to acquire a large variety of animals, and all beautiful animals too. He has a long and brilliant life, and his children and animals are such that he becomes famous for them. His achievements also mark him as a great person.

Word-for-word explanation:

Saḥ yaḥ evam etat vairūpam parjanye protam veda, he who knows that this [Sāma called] Vairūpa is rooted in the clouds; virūpān ca surūpān ca paśūn avarundhe, he comes to possess a large variety of animals and beautiful animals also; sarvam āyuḥ eti, he lives the full span of his life; jyok jīvati, he has a brilliant life; mahān prajayā paśubhiḥ bhavati, he becomes famous for his children and for his animal wealth; mahān kīrtyā, he is renowned for his achievements; varṣantam na nindet tat vratam, his vow is not to criticize the clouds that pour rain. Iti pañcadaśaḥ khaṇḍaḥ, here ends the fifteenth section.

Commentary:

It is a characteristic of those who worship the Sāma that they never find fault with others. This is why they do not say anything bad about even the clouds that give rain.