[IDEM libro quinto posteriorum a Iauoleno epitomatorum. ] §19.1.51.prSi et per emptorem et uenditorem mora fuisset, quo minus uinum praeberetur et traderetur, perinde esse ait, quasi si per emptorem solum stetisset: non enim potest uideri mora per uenditorem emptori facta esse ipso moram faciente emptore.
[THE SAME in the fifth book of Posteriora epitomized by Javolenus] If there has been delay on the part of both the buyer and the seller, preventing the wine from being supplied and delivered, he (Labeo) says that it is just as if the delay had been on the part of the buyer alone; for delay cannot be deemed to have been caused to the buyer by the seller when the buyer himself is causing delay.
§19.1.51.1Quod si fundum emisti ea lege, uti des pecuniam kalendis Iuliis, et si ipsis calendis per uenditorem esset factum, quo minus pecunia ei solueretur, deinde per te staret quo minus solueres, uti posse aduersus te lege sua uenditorem dixi, quia in uendendo hoc ageretur, ut, quandoque per emptorem factum sit, quo minus pecuniam soluat, legis poenam patiatur.
But if you have bought a tract of land on the condition that you should pay the money on the Calends of July, and if on the Calends themselves it was due to the seller that the money was not paid to him, and subsequently it was due to you that you did not pay, I have said that the seller can avail himself of his condition against you, because in the sale this was intended: that whenever it should be due to the buyer that he does not pay the money, he should suffer the penalty of the condition.
hoc ita uerum puto, nisi si quid in ea re uenditor dolo fecit.
I think this is true only if the seller has not acted with dolo (fraud or bad faith) in the matter.