The book Hindu Dharma (comprised of speeches given by Chandrashekarendra Saraswati) states in this chapter that:
The Taittiriya Brahmana has it that to extinguish the agnihotra fire is to earn the demerit of killing a hero.
I want to know which verse speaks of the above mentioned statement?
I think it's Taittirīya Saṃhitā (TS 1.5.2.1) not the Brāhmaṇa you are referring to.
Translation of the verse from here:
i. 5. 2.
He who removes the fire casts away the sacrifice and cattle. The sacrificial cake is offered on five potsherds; the sacrifice is fivefold, cattle are fivefold; verily he wins the sacrifice and cattle. Now he who removes the fire is the slayer of the hero among the gods; Brahmans desirous of holiness did not aforetime eat his food; the Yajyas and Anuvakyas are in the Pankti metre; the sacrifice is fivefold, man is fivefold; verily making recompense to the gods for the hero he re-establishes the fire [1].
Sanskrit (IAST) verse from here:
Paragraph: 2
Verse: 1
Sentence: 1 párā vā́ eṣá yajñám paśū́n vapati yò 'gním udvāsáyate /
Sentence: 2 páñcakapālaḥ puroḍāśo bʰavati
Sentence: 3 pā́ṅkto yajñáḥ pā́ṅktāḥ paśávo yajñám evá paśū́n ávarunddʰe /
Sentence: 4 vīrahā́ vā́ eṣá devā́nāṃ yò 'gním udvāsáyate
Sentence: 5 ná vā́ etásya brāhmaṇā́ r̥tāyávaḥ purā́nnam akṣan /
Sentence: 6 paṅktyò yājyānuvākyā̀ bʰavanti
Sentence: 7 pā́ṅkto yajñáḥ pā́ṅktaḥ púruṣo devā́n evá vīráṃ niravadā́yāgním púnar ā //
Also see: What is Virahatya (Killing of a hero)?
