There are generalities [shared between them] and specifics [unique to each of them]. Shirk is more general than kufr, for every mushrik is a kāfir but not every kāfir is a mushrik.
The parable of those who disbelieve in their Lord is that their works are as ashes, on which the wind blows furiously on a stormy day, they shall not be able to get aught of what they have earned.
The origin, starting point of Bid’ah is revilement of the Sunnah by (one’s) suspicion and desire, just as Ibless reviled the command of His Lord with his opinion and desire.
Four [affairs] of Jāhiliyyah that the people will not leave: Wailing over the dead; reviling ancestors; tying rain to the rising or setting of stars, and contagion.
It has been stated by more than one among the People of Knowledge about this ḥadīth and what resembles it from the narrations, such as the Attributes, and the descent of our Lord [twt] to the lowest heaven every night. So they say: ‘Affirm these narrations, have faith in them, do not deny them, nor ask how.’