Reference for Menachot 179:19
רבי חייא בר יוסף אמר בירוצי מדות ר' יוחנן אמר כאותה ששנינו המקבל עליו לספק סלתות מארבע ועמדו בשלש יספק מארבע
What is meant by 'the surplus of the drink-offerings'? - R'Hiyya B'Joseph said, It is the overflow of the measures. R'Johanan said, It is as we have learnt:<span class="x" onmousemove="('comment',' Shek. IV, 9; B.M. 57b.');"><sup>22</sup></span> If a man had undertaken to supply fine flour at four [se'ahs a sela']<span class="x" onmousemove="('comment',' And he was paid by the Temple-treasurer a certain sum of money.');"><sup>23</sup></span> and the price subsequently stood at three [se'ahs a sela'], he must still supply it at four;<span class="x" onmousemove="('comment',' For in regard to Temple matters the payment of money binds the contract even though the goods have not yet passed either actually or symbolically into the possession of the Temple.');"><sup>24</sup></span>