"I said: 'O Messenger of Allah (ﷺ)! What is the worst sin?' He said: 'That you make and equal to Allah, while it is He who created you.'" He said: "I said: 'Then what?' He said: 'That you kill your child fearing that he will eat with you.'" He said: "I said: 'Then what?' He said: 'That you commit adultery with your neighbors wife.'"
Jami` at-Tirmidhi Book 47, Hadith 234
← Previous Hadith "When my innocence was revealed, the Messenger of Allah (ﷺ) stood on the Minbar and mentioned that. He recited the Qur'an, and when he descended, he ordered that two men, and the woman, be beaten as their Hadd."

Jami` at-Tirmidhi Book 47, Hadith 233 Next Hadith → "I asked the Messenger of Allah (ﷺ) which sin is the worst.' He said: 'That you make an equal to Allah while it is He who created you, that you kill your child so that he not eat with you - or because of your food, that you commit adultery with your neighbor's wife.'" He said: "And he recited this Ayah: 'And those who invoke not any other god along with Allah, nor kill such life as Allah has forbidden, except for what is required, nor commit illegal sexual intercourse - and whoever does that shall receive punishment. The torment will be doubled for him on the Day of Resurrection, and he will abide therein in disgrace (25:68 & 69).'"

Jami` at-Tirmidhi Book 47, Hadith 235