Allaah (The Most High said:
أَمۡ كُنتُمۡ شُہَدَآءَ إِذۡ حَضَرَ يَعۡقُوبَ ٱلۡمَوۡتُ إِذۡ قَالَ لِبَنِيهِ مَا تَعۡبُدُونَ مِنۢ بَعۡدِى قَالُواْ نَعۡبُدُ إِلَـٰهَكَ وَإِلَـٰهَ ءَابَآٮِٕكَ إِبۡرَٲهِـۧمَ وَإِسۡمَـٰعِيلَ وَإِسۡحَـٰقَ إِلَـٰهً۬ا وَٲحِدً۬ا وَنَحۡنُ لَهُ ۥ مُسۡلِمُونَ
”Or were you witnesses when death approached Ya’qub (Jacob)? When he said unto his sons, “What will you worship after me?” They said, “We shall worship your Ilah (God – Allah), the Ilah (God) of your fathers, Ibrahim (Abraham), Isma’il (Ishmael), Ishaque (Isaac), One Ilah (God), and to Him we submit (in Islam).” [2:133]
They responded to their father with what was a source of comfort for the eyes.
They mentioned Tawheed and Deeds (in their response).
[For further details, see Tayseer Al-Kareem Ar-Rahmaan
Fee Tafseer Kalaam Al-Mannaan of Imaam (rahimahullaah)