וְעַתָּ֖ה אָר֣וּר אָ֑תָּה מִן־הָֽאֲדָמָה֙ אֲשֶׁ֣ר פָּצְתָ֣ה אֶת־פִּ֔יהָ לָקַ֛חַת אֶת־דְּמֵ֥י אָחִ֖יךָ מִיָּדֶֽךָ׃
E agora você é amaldiçoado pela terra, que abriu sua boca para receber os sangues de seu irmão de sua mão.
Or HaChaim
Cain was jealous of Abel because he thought that Abel's existence was the cause that he himself had been degraded. He thought that his own shortcomings had come to light only by comparing him to his brother. Once his brother would be out of the way G'd would have to turn to him seeing there was no one else to turn to. This is why he planned to kill Abel. He realised that the stench of Abel's decaying body would rise heavenwards. Inasmuch as man had been forbidden to murder, Cain sought a way of killing Abel without laying a hand on him. We have heard that Cain was a man of the earth; he was familiar with how the earth functioned. Our sages (compare Nedarim 39) say that earth has limbs just like a human being, i.e. the equivalent of hands, feet, etc. Cain knew which part of the earth served as its mouth, its eyes, etc. As a result of this familiarity with the earth he found a way to kill Abel with guile without actually laying a hand on him. The Torah describes that while Cain and Abel walked in the field Cain found a suitable spot to carry out his evil plan. The word ויקם is not part of the act of murder. It means he simply stood over him in a spot where the earth would swallow him. The earth actually did the killing. While the Torah does not spell out the exact nature of Abel's death in our verse, it does so in verse 11.
Rabbeinu Bahya
נטית ימיך תבלעמו ארץ, “when You inclined Your right hand the earth swallowed them.” Pirke d'Rabbi Eliezer chapter 17 use this verse to prove that the Egyptians were granted burial in the earth. This was in recognition of their having accompanied Yaakov on the long journey to the land of Canaan at the time he was buried. Mechilta Shirah section 9 adds: ”the word ימין or ימינך when referring to G’d always refers to an oath G‘d has sworn. We know this from Isaiah 62,8: ‘The Lord has sworn with His right hand.’ The meaning of all this is that whereas the sea had spat out the bodies of the Egyptians who had been drowned in it, the earth refused to accept these bodies remembering G’d had cursed it for accepting Hevel’s body at the time (Genesis 4,11). It continued in its refusal until G’d swore an oath that He would not demand an accounting from earth for accepting these bodies. This accounts for the words נטית ימינך תבלעמו ארץ, ‘after You gave a signal with Your right hand the earth swallowed them.’”
Radak
ועבודה רבה, he also engaged extensively in agriculture. Compare Proverbs 12,11, עובד אדמתו, “tilling his own land.” Compare also Genesis 4,11 כי תעבוד את האדמה, “when you till the soil.”