"Thus shall you say to the house of Jacob and declare to the children of Israel." It is a known fact that the word "house" is used to refer to assembly and unity, as we interpret "It shall be eaten in one house" to mean 'in one group'. Our sages, of blessed memory, said that the name Jacob is used when they (the People of Israel) do not do the will of the LORD, and the name Israel is used when they do His will. This is the sense in which "Thus shall you say" is said – in gentle words to those called the house of Jacob, meaning that despite their being called the house of Jacob for not having yet repented, unified and become one house, speak to them in gentle words. But "And declare", means harsh words, and is used to refer to the children of Israel when they are being called "the children Israel", for despite that they do His will and are called by the name Israel, since they are not unified and are being named children of Israel in the plural, speak to them in harsh words.