Reference for Pesachim 27:3
הוסיף ר' עקיבא ואמר מימיהם של כהנים לא נמנעו מלהדליק את השמן שנפסל בטבול יום בנר שנטמא בטמא מת אף על פי שמוסיפין טומאה על טומאתו
THE SEGAN<span class="x" onmousemove="('comment',' Chief of the priests and deputy High-Priest, v. Sanh., Sonc. ed. p. 97. n. 1.');"><sup>2</sup></span> OF THE PRIESTS, SAID: DURING THE DAYS OF THE PRIESTS THEY NEVER REFRAINED FROM BURNING [SACRIFICIAL] FLESH WHICH HAD BEEN DEFILED BY A DERIVATIVE UNCLEANNESS WITH FLESH WHICH HAD BEEN DEFILED BY A PRINCIPAL UNCLEANNESS, THOUGH UNCLEANNESS IS ADDED TO ITS UNCLEANNESS.<span class="x" onmousemove="('comment',' The following degrees of defilement are distinguished: (i) The super principal (lit. , 'father of fathers' of) defilement, which is that borne by a corpse; (ii) principal (lit. , 'the father of') defilement, which is that of a human being or a utensil 'defiled by a corpse; (iii) derivative (lit., 'offsp of') defilement, borne by a human being, utensil or food which is contaminated by a principal defilement - this is also known as the first degree or 'beginning' of defilement; (iv) the second degree of defilement, which is that of food contaminated by a principal defilement. In hullin there is nothing further, and if hullin comes into contact with something unclean in the second degree it remains clean. Terumah, however, is liable to (v) a third degree, but no further. Sacred food, i.e., the flesh of sacrifices, is liable to (vi) a fourth degree of defilement. Third degree terumah and fourth degree sacred flesh are called 'unfit' but not unclean, because they cannot communicate uncleanness to their own kind, i.e., to terumah and sacred flesh respectively.');"><sup>3</sup></span>