The ruling on vowing to slaughter a sheep annually and specifying its color

The questioner:
My brother, my mother, may Allah reward you with good, made a vow regarding my younger brother. It is annual, every year, meaning she slaughters a sacrifice for the vow, and she specified the color. I do not know if it is obligatory or not.

The Shaykh:
What did she say?

The questioner:
What did she say in the vow?

The Shaykh:
Come on, tell us.

The questioner:
She said it was for the face of Allah the Exalted. The boy had an illness, a fit, I do not know what it was. She said, "Come on, O Lord, for Your face, if You cure this boy, if Allah wills, for Your face, I will slaughter a sheep as a thanksgiving, annually, every year, continuously." Yes, she said if the boy recovers, O Shaykh, she will slaughter a sheep throughout the year.

The Shaykh:
She is required to fulfill the vow, if she is able, she is required to fulfill the vow. Allah the Exalted said: “They fulfill their vows,” and the Messenger (peace and blessings be upon him) said: Yes.

The presenter:
Abu Yusuf, Abu Yusuf.

The questioner:
Is the color obligatory or not? The color?

The presenter:
If you specified the color, Shaykh Salih?

The Shaykh:
The color is not obligatory, but it is obligatory that it be free from diseases and defects, and that it also not be emaciated or old, decrepit. Yes.

The presenter:
Thank you, Sa'd from al-Ta'if. Please, Sa'd.