I asked Allah's Messenger (ﷺ) "What is the biggest sin in the sight of Allah?" He said, "To set up rivals unto Allah though He alone created you." I said, "In fact, that is a tremendous sin," and added, "What next?" He said, "To kill your son being afraid that he may share your food with you." I further asked, "What next?" He said, "To commit illegal sexual intercourse with the wife of your neighbor."
Sahih al-Bukhari Book 97, Hadith 145
← Previous Hadith Once the Prophet (ﷺ) was preaching while a bedouin was sitting there. The Prophet (ﷺ) said, "A man from among the people of Paradise will request Allah to allow him to cultivate the land Allah will say to him, 'Haven't you got whatever you desire?' He will reply, 'yes, but I like to cultivate the land (Allah will permit him and) he will sow the seeds, and within seconds the plants will grow and ripen and (the yield) will be harvested and piled in heaps like mountains. On that Allah will say (to him), "Take, here you are, O son of Adam, for nothing satisfies you.' "On that the bedouin said, "O Allah's Messenger (ﷺ)! Such man must be either from Quraish or from Ansar, for they are farmers while we are not." On that Allah's Messenger (ﷺ) smiled .

Sahih al-Bukhari Book 97, Hadith 144 Next Hadith → Two person of Bani Thaqif and one from Quarish (or two persons from Quraish and one from Bani Thaqif) who had fat bellies but little wisdom, met near the Ka`ba. One of them said, "Did you see that Allah hears what we say? " The other said, "He hears us if we speak aloud, but He does not hear if we speak in stealthy quietness (softly)." The third fellow said, "If He hears when we speak aloud, then He surely hears us if we speak in stealthy quietness (softly)." So Allah revealed the Verse:-- 'And you have not been screening against yourselves, lest your ears, and your eyes and your skins should testify against you..." (41.22)

Sahih al-Bukhari Book 97, Hadith 146