The verse names vacika-tapas. Vakyam — speech that is satyam, priya-hitam — true, agreeable, beneficial. Svadhyaya-abhyasanam — practice of svadhyaya. Van-mayam tapah uchyate — this is called speech-tapas.
Krishna names four marks of austere speech plus the shastric svadhyaya. Speech that does not agitate, that is true, agreeable, and beneficial — and that practices the recitation of one's Veda — is the body's tapas in its verbal register.
Shankara reads speech free from causing agitation to any being, that is truthful, and simultaneously agreeable and genuinely beneficial — these four qualifications must all be present together, not merely one or two. A statement satisfying only some is not verbal austerity. Additionally, regular svadhyaya-abhyasana is named: the practice of recitation of one's branch of the Veda. The four-fold criterion holds the speaker to a high standard: any defect in any of the four cancels the tapas.
Madhusudana carefully distinguishes the four qualifications: anudvega-karam means 'not causing sorrow to anyone.' Satyam means 'grounded in pramana — valid means of knowledge — conveying abadhita-artham — uncontradicted meaning.' Priyam means 'pleasing to the hearer at the moment of hearing.' Hitam means 'productive of welfare upon maturation.' The conjunction — chakara — gathers all four into a single requirement. The bhakta's speech-tapas requires all four simultaneously.
Ramanuja reads speech directed toward others that does not cause disturbance, that is true, agreeable, beneficial, along with svadhyaya-abhyasana. Speech becomes kainkarya offered to Bhagavan when it satisfies these criteria.
Ramanuja's brevity is itself significant: speech as kainkarya is not elaborated but quietly affirmed; every syllable can be relational worship if the four criteria hold.
Madhva reads speech that neither agitates nor misleads as van-maya tapas. For the paratantra-jiva, every utterance is either an expression of correct subordination to svatantra Hari or a deviation from it. Speech that causes udvega is the deviation; speech that is satya, priya, hita is the alignment. Svadhyaya-abhyasana is the bhakta's verbal discipline that grounds his speech in the shruti's structure. The bheda-frame: the four criteria are real distinctions, the speech-tapas is real practice.
Vallabha's commentary on this verse is not extant in the transmitted panel; in pushti-marga, verbal austerity is not effort but prasada — speech becomes tapas only when it flows as Krishna-arpana. Anudvega-karam speech is the natural outflow of a soul steeped in Krishna's lila; truth, agreeableness, benefit arise not by discipline alone but by grace's settling in the bhakta. The pushti-marga reading: when the bhakta's heart is full of Krishna, the four criteria emerge naturally.
Shridhara defines vachika-tapas through four precise marks: non-agitation — udvegam bhayam na karoti iti anudvega-karam; truthfulness — satyam; agreeableness — priyam, pleasing to the hearer at the moment of hearing; benefit — hitam, that which causes happiness upon maturation, parinama-sukhakaram. Vedabhyasa is also vachika-tapas. The bhakta's speech-discipline is now precisely characterized.