Complete Passuk
וַיֹּ֖אמֶר מֶ֣ה עָשִׂ֑יתָ ק֚וֹל דְּמֵ֣י אָחִ֔יךָ צֹעֲקִ֥ים אֵלַ֖י מִן־הָֽאֲדָמָֽה׃
Chabad / Judaica Press
Chazal
Chazalקוֹל דְּמֵי אָחִיךָ — דַּם אָחִיךָ לֹא נֶאֱמַר אֶלָּא דְּמֵי אָחִיךָ, מְלַמֵּד שֶׁהָיָה דָּמוֹ מֻשְׁלָךְ עַל הָעֵצִים וְעַל הָאֲבָנִים.
“The voice of your brother’s bloods” — it does not say “blood” but “bloods”; this teaches that his blood was cast upon the trees and upon the stones.
On the daf / in context: The plural also describes the scattered state of the blood after the murder.
Type of Learning: Custom (scattered blood)
What Is Learned: Hevel’s blood was strewn upon the trees and the stones.