Kauthumagrihyasutra 1

Now then, the expiations.
Now then, for the order of ceremonies: either a householder or a Vedic student; a householder in the domestic fire, a Vedic student in the common fire. In the householder's rituals, whether in serving [the fire] or when the studentship is broken, the occasional rite preceded by the morning oblation is to be performed in the common fire.
In the case of re-establishment of the fire, he should avoid [the fire of another]; beginning in the evening, if an expiation for the particular occasion is incurred, the rite is to be performed by both of them there.
If the oblation has lapsed on the full-moon day, they should perform those respective rites with both [oblations]; and if on a joint day, he should perform it having combined [them]; in the absence of that, he should perform it immediately; but on the subsequent new-moon day, there is an expiation. For three nights or five nights, or from midnight, those [oblations] preceded by an expiation sacrifice—both of them should sacrifice, having combined both joint days; when those two rites have lapsed, similarly in that case, if there is an omission or if it has lapsed beyond a month, they should perform the re-establishment of the fire.
For the sake of expiation, either a Prājāpatya penance [is performed]; and further there is a particular rule: if one touches the domestic fire in the house-fire, in that ritual either one is to be performed; he should recite both of the mantras; taking [the wood] connected with those kindling sticks, the ritual then is descent [of the fire]; they should perform breath-control.
Having sprinkled [water] silently, having worshipped with the mantra, upon the mystic utterance […] both of them, having laid on two kindling sticks, he should recite the mantra for the offering rite.
Here the cake is to be made silently, or the wife [does it]; thus equally they should perform the internalisation of the sacred fire. Or rather, it must be performed; he is individually one requiring expiation; beyond that, there should be a particular rule; if [the fire] is in another fire, it is to become our own; similarly, one should perform the descent of the sacrificial [fire]; the initial internalisation of the sacred fire is well known; having released that […], you should say: “Bhūr bhuvas svar”.
Standing silently, he should not go away; in that keeping of the fire […] having failed in the rite; in one’s own domestic fire, he is individually one requiring expiation; beyond this, there is a particular rule: if there is no internalisation according to the procedures of the clarified butter offerings, [then] the internalisation is well known; having begun again, whatever rite from the morning oblation up to the introductory formula might be omitted, if it is the morning oblation, some say there is an expiation; repetition of a deficient rite and the like; beyond the primary rite there is expiation; beyond this, the particular rule is explained next according to the ritual procedure for cooked mess; in a place sloping towards the north-east, there he should smear the sacrificial ground.

KauthGS 2: