Is there a legal prohibition in saying (O Allah, send blessings upon the spirit of the Prophet Muhammad)?

The questioner:
May Allah reward you, O Shaykh. Now, the second question, O Shaykh: a phrase has spread among people where they say, "Send blessings upon the spirit of the Prophet (peace and blessings be upon him)."

The Shaykh:
No, send blessings upon the Prophet; it does not need to be directed to his spirit. Send blessings upon the Prophet, send blessings upon the Prophet; there is no need to say "spirit."

The questioner:
O Allah, send blessings and peace, but what is the ruling on this phrase, O Shaykh, that it is being used?

The Shaykh:
It is a garment, but leaving it is better. Say, "O Allah, send blessings upon the Messenger of Allah."

The questioner:
Otherwise, there is nothing transmitted regarding this phrase, O Shaykh.

The Shaykh:
The point is, absolutely not; but this expression has no limit.

The questioner:
Yes, I mean, it is better to leave it, O Shaykh.

The Shaykh:
Yes, it is obligatory.

The questioner:
Yes, and we do not say that it is forbidden.

The Shaykh:
No, by Allah, he does not pray, but it is obligatory to leave it, because it is an innovation, and the Messenger said, "Say, O Allah, send blessings upon Muhammad," and not "upon the spirit of Muhammad."

The questioner:
Okay, O Shaykh, if it is an innovation, is it forbidden, O Shaykh, if it is an innovation?

The Shaykh:
He asks: Is the prohibition because we are ignorant, or is it just that it should be avoided?

The presenter:
May Allah preserve you. This call was to the Honorable Shaykh 'Uthaymin ibn Baz on the evening of Tuesday at the end of the month of Shawwal in the year 1466 AH.