In return for Indra’s benediction that their branches and twigs would grow back when trimmed, the trees accepted one fourth of the reactions for killing a brāhmaṇa. These reactions are visible in the flowing of sap from trees. [Therefore one is forbidden to drink this sap.]
Srimad Bhagavata Purana
श्रीमद्भागवतमहापुराणम्
मूल श्लोकः
ईरिणं ब्रह्महत्याया रूपं भूमौ प्रदृश्यते । तुर्यं छेदविरोहेण वरेण जगृहुर्द्रुमाः
īriṇaṃ brahmahatyāyā rūpaṃ bhūmau pradṛśyate | turyaṃ chedaviroheṇa vareṇa jagṛhurdrumāḥ
SB 6.9.8