When anyone of you intends to sacrifice the animal

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].

عن أم سلمة رضي الله عنها قالت قال رسول الله صلى الله عليه وسلم ‏:‏ ‏ "‏من كان له ذبح يذبحه، فإذا أهل هلال ذي الحجة، فلا يأخذن من شعره ولا من أظفاره شيئًا حتى يضحي‏"‏ ‏(‏‏(‏رواه مسلم‏)‏‏)‏‏.‏