The ideal way to send blessings upon the Prophet (blessings and peace of Allah be upon him

Praise
be to Allah.

Sending blessings upon the
Prophet (blessings and peace of Allah be upon him) is one of the greatest
acts of worship encouraged in Islam, and it is one of the most beneficial
supplications for a person in this world and the hereafter, and it is one of
the requirements of loving, venerating and respecting the Prophet (blessings
and peace of Allah be upon him) and giving him his rights. 

With regard to the ideal way of
sending blessings upon the master of mankind (blessings and peace of Allah
be upon him), there are a number of ways of doing that, which you can find
in the book Sifat Salaat an-Nabi (sall-Allahu ‘alayhi wa sallam) by
al-‘Allaamah al-Albaani (may Allah have mercy on him), p. 165 of the edition
published by Maktabat al-Ma ‘aarif in Riyaadh [this book is available in
English as The Prophet’s Prayer Described]. Among the soundest and
most well-known of these ways are the two ways that the Prophet (blessings
and peace of Allah be upon him) taught his Companions (may Allah be pleased
with them) when they asked him how they should send blessings upon him
(blessings and peace of Allah be upon him). These two ways are as follows: 

~1~

“Allaahumma salli ‘ala
Muhammad wa ‘ala aali Muhammad kama salayta ‘ala Ibraaheem wa ‘ala aali
Ibraaheem, innaka hameedun majeed. Allaahumma baarik ‘ala Muhammad wa ‘ala
aali Muhammad kama baarakta ‘ala Ibraaheem wa ‘ala aali Ibraaheem, innaka
hameedun majeed (O Allaah, send prayers upon Muhammad and upon the
family of Muhammad, as You sent prayers upon Ibraaheem and upon the family
of Ibraaheem; You are indeed Worthy of Praise, Full of Glory. O Allaah, send
blessings upon Muhammad and upon the family of Muhammad as You sent
blessings upon Ibraaheem and upon the family of Ibraaheem; You are indeed
Worthy of Praise, Full of Glory).”

Narrated by al-Bukhaari (3700)
and Muslim (406) from the hadeeth of Ka‘b ibn ‘Ajrah (may Allah be pleased
with him). 

~2~

“Allaahumma salli ‘ala
Muhammadin wa ‘ala azwaajihi wa dhurriyyatihi kama salayta ‘ala Ibraaheem,
wa baarik ‘ala Muhammadin wa ‘ala azwaajihi wa dhurriyyatihi kama baarakta
‘ala aali Ibraaheem, innaka hameedun majeed (O Allaah, send Your
salaah (grace, honour and mercy) upon Muhammad and upon his wives and
offspring, as You sent Your salaah upon Ibraaheem, and send Your
blessings upon Muhammad and upon his wives and offspring, as You sent Your
blessings upon the family of Ibraaheem. You are indeed Praiseworthy, Most
Glorious).” 

Narrated by al-Bukhaari (3369)
and Muslim (407) from the hadeeth of Abu Humayd as-Saa‘idi (may Allah be
pleased with him). 

The Prophet (blessings and peace
of Allah be upon him) did not choose anything but that which is noblest and
best. 

See: Rawdat at-Taalibeen
by an-Nawawi (11/66); Fath al-Baari by Ibn Hajar (11/166); Sifat
Salaat an-Nabi (sall-Allahu ‘alayhi wa sallam) by al-Albaani, p. 175;
al-Mawsoo‘ah al-Fiqhiyyah al-Kuwaitiyyah, 27/97 

It is better to vary the phrases
used, switching between the versions that have been narrated, sometimes
reciting one and sometimes reciting another, so as to follow the Sunnah and
sharee‘ah, and so that always reciting one version does not lead to
neglecting another which is also proven, and because there are many other
benefits in doing so which will not be attained by always reciting only one
and not the other. 

But we should point out that it
is not prescribed to combine and mix these phrases so as to produce a
combination of all of them in one; rather that is contrary to the Sunnah, as
was stated by a number of scholars.

See: Majmoo‘ al-Fataawa
by Ibn Taymiyyah (22/335, 458; 24/242, 247); Jala’ al-Ifhaam by Ibn
al-Qayyim (p. 373 ); Qawaa‘id Ibn Rajab (p. 14); ash-Sharh al-Mumti‘
by Ibn ‘Uthaymeen (2/56, 65; 3/29, 98). 

All of this has to do with
sending blessings upon him (blessings and peace of Allah be upon him) after
the Tashahhud in the prayer. 

With regard to sending blessings
upon him (blessings and peace of Allah be upon him)) by saying “Allahumma
salli ‘ala Muhammadin wa aali Muhammad (O Allah, send blessings upon
Muhammad and the family of Muhammad) outside of the prayer, if what your
friend means is that it is lacking in comparison to the complete wording
that has been narrated, then this is correct. But if what he meant was that
it is not valid or that it does not count as sending blessings upon the
Messenger (blessings and peace of Allah be upon him), then that is not the
case; rather it is sending blessings upon the Prophet (blessings and peace
of Allah be upon him) and its wording is correct and fulfills the purpose.
The scholars still say, “Allahumma salli ‘ala Muhammad” or “sall-Allahu
‘alayhi wa sallam (may Allah send blessings and peace upon him)” and the
like. The matter is broad in scope, in sha Allah. 

Al-Haafiz ibn Hajar stated in
Fath al-Baari (11/166) that the majority of scholars think that any
wording that fulfills the purpose of sending blessings upon him is
acceptable, but in the prayer one should keep to the wording that has been
narrated and not omit any part of it, so as to be sure of following the
Sunnah and what is narrated from the Prophet (blessings and peace of Allah
be upon him). 

With regard to this wording
also, it is restricted to sending blessings (salaah) and not salaam, whereas
Allah, may He be glorified, has instructed us to send both blessings and
greeting of peace upon him, as He says (interpretation of the meaning):

“Allah sends His Salat (Graces,
Honours, Blessings, Mercy, etc.) on the Prophet (Muhammad SAW) and also His
angels too (ask Allah to bless and forgive him). O you who believe! Send
your Salat on (ask Allah to bless) him (Muhammad SAW), and (you should)
greet (salute) him with the Islamic way of greeting (salutation i.e. As-Salamu
Alaikum)”

[al-Ahzaab 33:56]. 

The scholars have stated that it
is makrooh for a person to always mention salaah (blessings) without salaam
(greeting of peace), or to always mention salaam without salaah. But if he
mentions both of them, or mentions salaah on its own sometimes, or salaam on
its own sometimes, then he is fallowing the verse. And Allah knows best.

See: Fath al-Baari,
11/167 

And Allah knows best.