SB 9.16.8

uttasthus te kuśalino
 nidrāpāya ivāñjasā
pitur vidvāṁs tapo-vīryaṁ
 rāmaś cakre suhṛd-vadham
Word for word: 
uttasthuḥ — got up immediately; te — Lord Paraśurāma’s mother and brothers; kuśalinaḥ — being happily alive; nidrā-apāye — at the end of sound sleep; iva — like; añjasā — very soon; pituḥ — of his father; vidvān — being aware of; tapaḥ — austerity; vīryam — power; rāmaḥ — Lord Paraśurāma; cakre — executed; suhṛt-vadham — killing of his family members.
Translation: 
Thereafter, by the benediction of Jamadagni, Lord Paraśurāma’s mother and brothers immediately came alive and were very happy, as if awakened from sound sleep. Lord Paraśurāma had killed his relatives in accordance with his father’s order because he was fully aware of his father’s power, austerity and learning.