Reference for Shabbat 3:5
הַמֵּחַם שֶׁפִּנָּהוּ, לֹא יִתֵּן לְתוֹכוֹ צוֹנֵן בִּשְׁבִיל שֶׁיֵּחַמּוּ, אֲבָל נוֹתֵן הוּא לְתוֹכוֹ אוֹ לְתוֹךְ הַכּוֹס כְּדֵי לְהַפְשִׁירָן. הָאִלְפָּס וְהַקְּדֵרָה שֶׁהֶעֱבִירָן מְרֻתָּחִין, לֹא יִתֵּן לְתוֹכָן תְּבָלִין, אֲבָל נוֹתֵן הוּא לְתוֹךְ הַקְּעָרָה אוֹ לְתוֹךְ הַתַּמְחוּי. רַבִּי יְהוּדָה אוֹמֵר, לַכֹּל הוּא נוֹתֵן, חוּץ מִדָּבָר שֶׁיֶּשׁ בּוֹ חֹמֶץ וְצִיר:
A meicham [a copper kettle placed on the fire to heat the water inside] — if it were removed [from the kirah, and it contained hot water], cold water should not be put into it to be heated [by the hot water remaining in the meicham, this being like cooking on the Sabbath], but one can put into it [much (cold) water, so that it all becomes lukewarm], or into a cup, in order to make it lukewarm. [And even though it is a kli-sheni ("second vessel"), it is permitted only to make it lukewarm. But it is forbidden to put in a little so that it is heated, this tanna holding that a kli-sheni cooks. And below it is taught: "But he may put it into the dish," which implies that a kli-sheni does not cook. The halachah is that a kli-sheni does not cook.] If one took an ilpass or a kederah (types of pots) [from the fire ben hashmashoth], boiling, he may not put spices into them, but he may put them into the dish or into the tamchui (into which the contents of the pots have been poured), [for a kli-sheni does not cook. ("tamchui":) a large tray into which the entire ilpass is poured, and thence apportioned to the dishes.] R. Yehudah says: He may put them into anything, [even a kli-rishon ("first vessel")], except one which contains vinegar or fish-brine, [for they cook the spices. The halachah is not in accordance with R. Yehudah. And it is specifically spices that it is forbidden to put into a kli-rishon, even after it is removed from the fire. But salt does not cook even in a kli-rishon, except when it is on the fire. Therefore, it is permitted to put salt even into a kli-rishon after it is removed from the fire.]