Umm Salamah (May Allah be pleased with her) said:
The Messenger of Allah (ﷺ) said, "When anyone of you intends to sacrifice the animal and enter in the month of Dhul-Hijjah, he should not get his hair cut or nails pared till he has offered his sacrifice."[Muslim]. (DE)
App reference (DE): Book 18, Hadith 196 (DE)
Arabic/English book reference (DE): Book 18, Hadith 1706 (DE)