הלכה על זבחים 200:16

To not eat the second tithe in bereavement: To not eat the second tithe in bereavement. And I have written the content of the second tithe in the Order of Reeh Anochi (Sefer HaChinukh 473). And the content of bereavement from Torah writ is that one who has one of his relatives die on him is obligated to mourn for them - that day that [the relative] dies and he buries him, he is called a bereaved (onen). And they, may their memory be blessed, said explicitly that only the day of death and burial is the main bereavement from Torah writ. And [that is] specifically the day, but not the night, as it is stated (Leviticus 10:19), "And I ate the sin-offering of the day" - and they, may their memory be blessed, expounded (Zevachim 100b), "'The day' is forbidden, but it is permitted at night." And about this is it stated (Deuteronomy 26:14), "I have not eaten from it in bereavement" - meaning to say that if he ate from it in bereavement, he would have transgressed. And it is not only second tithes that it is forbidden to eat in bereavement, but rather one who eats any consecrated foods in bereavement is lashed for them (Mishneh Torah, Laws of Second Tithes and Fourth Year's Fruit 3:7).