Gobhilagrihyasutra 1.5.26

1.5.26

athā 'parāhṇa evā ''plutyau 'pavasathikaṃ dampatī bhuñjīyātāṃ, yad enayoh kāmyaṃ syāt, sarpirmiśraṃ syāt, kuśalena.

In the afternoon husband and wife, after having bathed, should eat fast-day food which is pleasant to them. It should contain butter (and should be prepared) in the due way.