How purification from the najaasah of a dog is done

Muslim (279) narrated
that Abu Hurayrah (may Allaah be pleased with him) said: The Messenger of
Allaah (peace and blessings of Allaah be upon him) said: “The
purification of the vessel of one of you, if a dog licks it, is to wash it
seven times, the first time with soil.” 

And Muslim (280) narrated that ‘Abd-Allaah ibn al-Mughaffal
said: The Messenger of Allaah (peace and blessings of Allaah be upon
him) said: “If a dog licks the vessel of one of you, let him wash it seven
times and rub it with soil the eighth time.” 

In these two ahaadeeth
the Prophet (peace and blessings of Allaah be upon him) explained how
purification from the najaasah of a dog is to be done, which is by washing
the vessel seven times, one of which should be with soil. Both are
required. 

Ibn Qudaamah (may Allaah have mercy on him) said in
al-Mughni (1/73): 

There is no difference of
scholarly opinion concerning the fact that the najaasah of a dog must be
washed seven times, one of which should be with soil. This is the view of
al-Shaafa’i. End quote. 

Al-Nawawi said in al-Majmoo’ (2/598): 

The scholars differed concerning the licking of a dog. Our
view is that it makes whatever it licked naajis (impure), and the vessel
must be washed seven times, one of which must be with soil. This is the view
of the majority of scholars. Ibn al-Mundhir narrated the view that it is
obligatory to wash it seven times from Abu Hurayrah, Ibn ‘Abbaas, ‘Urwah ibn
al-Zubayr, Tawoos, ‘Amr ibn Dinar, Maalik, al-Awzaa’i, Ahmad, Ishaaq, Abu
‘Ubayd and Abu Thawr. Ibn al-Mundhir said: This is also my opinion. End
quote. 

Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him) said: 

If the najaasah is somewhere other than on the ground and it
is the najaasah of a dog, then it must be purified by washing it seven
times, one of which must be with soil. End quote. 

Majmoo’ Fataawa Ibn ‘Uthaymeen
(11/245). 

It is better if the first
washing is the one that is done with soil, but if it is done otherwise that
still achieves the purpose and purifies the place. 

Al-Nawawi said in al-Majmoo’ (2/598): 

It is mustahabb to use the soil in the first washing, and if
that is not done then it is better to do it in any other time other than the
seventh. But if it is done in the seventh it is permissible. It says in the
reports in the Saheeh: “seven times” and “seven times, the first time
with soil”; in one report it says “the last time” instead of “the first
time.” In other reports it says, “seven times, the seventh with soil” and
“seven times and the eighth time sprinkle it with soil.” Al-Bayhaqi and
others narrated all these reports, which indicates that it is not essential
that it be done the first time, rather that it be done one of those times.
End quote. 

Washing with soil may be done in several ways: 

1-    
Washing with water then
sprinkling soil on it

2-    
Sprinkling soil on it and
following it with water

3-    
Mixing soil with water and
washing the vessel with it. 

This was stated by Shaykh Ibn ‘Uthaymeen in Sharh Buloogh
al-Maraam, hadeeth no. 14.