Verse 1.3.1.20

athājyamādāya prāṅudāharati | tadāhavanīye'dhiśrayati yasyāhavanīye havīṃṣi śrapayanti sarvo me yajña āhavanīye śṛto'sadityatha yadamutrāgre'dhiśrayati patnīṃ hyavakāśayiṣyanbhavati na hi tadavakalpate yatsāmi pratyggharetpatnīmavakāśayiṣyāmītyatha yatpatnīṃ nāvakāśayedantariyāddha yajñātpatnīṃ tatho ha yajñātpatnīṃ nāntareti tasmādu sārdhameva vilāpya prāgudāharatyavakāśya patnīṃ yasyo patnī na bhavatyagra eva tasyāhavanīye 'dhiśrayati tattata ādatte tadantarvedyāsādayati

Preview of English translation:

20. Having then taken up the butter (from the ground), he (the Agnidhra) carries it eastwards. In the case of one whose Ahavaniya fire is used for the cooking, he (now in the first place) puts it on the Ahavaniya, thinking, “My oblation shall be entirely cooked on the Ahavaniya!” The reason why he first puts it thereon (viz. on the Garhapatya) is, because he will have to make the wife look at it: for it would not be proper, if he were to take it (from the Ahavaniya) to the west in the midst of the performance, for the purpose of making the wife look at it; and if he were not to let the wife look at it at all, he would thereby exclude her from the sacrifice. And in this way, then, he does not exclude the (sacrificer's) wife from the sacrifice: therefore he does not take it eastwards till after melting it close by the wife (on the Garhapatya), and making her look at it. In the case of one who (through death or from other causes) has not his wife with him, he puts it from the very beginning on the Ahavaniya. He then takes it again from thence and puts it down within the altar.

For a detailled translation, including proper diacritics and footnotes, go the full English translation.