Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 21: The Anger and Appeasal of Viśvāmitra
Text 1.21.8

संश्रुत्यैवं करिष्यामीत्यकुर्वाणस्य राघव।
इष्टापूर्तवधो भूयात्तस्माद्रामं विसर्जय॥

saṁśrutyaivaṁ kariṣyāmīty akurvāṇasya rāghava
iṣṭāpūrta-vadho
bhūyāt tasmād rāmaṁ visarjaya

saṁśrutya = [for a person who] has promised and; evam = so; kariṣyāmi iti = I shall do; akurvāṇasya = who does not do so; rāghava = O descendant of Raghu; iṣṭāpūrta-vadhaḥ bhūyāt = the piety due to his iṣṭa and pūrta acts will be cancelled; tasmāt = therefore; rāmam = Rāma; visarjaya = please send.

O descendant of Raghu, [for a person who] has promised, “I shall do so” and who does not do so, the piety due to his iṣṭa and pūrta acts will be cancelled. Therefore, please send Rāma.

Iṣṭa pious activities are sacrifices culminating in the Aśvamedha. Pūrta pious activities refer to construction of ponds and the like.

vāpī-kūpa-taṭākādi-pratiṣṭhā-setu-bandhanam
anna-pradānam
ārāmaḥ pūrtam ity abhidhīyate

“Construction of ponds, wells, pools and so on as well as bridges and dams, distribution of foodstuffs and (setting up) parks for leisure are known as pūrta.”

NOTE. Restricting one’s speech to speaking only words that are truthful is one of the austerities of speech, according to Bhagavad-gītā 17.15: satyam... vāṅmayaṁ tapa ucyate.