Should he focus on purifying his heart or ondoing naafil acts?

Which is more important– dealing with feelings and thoughts that
Allaahdislikes, such as destructive envy, hatred,arrogance, showing
off, thinking highly of one's deeds, hard-heartedness, etc., which
form the evil that resides in the heart, or focusing on doing outward
naafil deeds such as prayer, fasting and other acts of worship and
fulfilling vows even though those other things are present in the
heart? Please advise us, may Allaah reward you with good.
Praise be to Allaah.
Some of the acts mentioned are obligatory, and those which are
obligatory should be given precedence, as Allaah says according to the
hadeeth qudsi narrated from His Messenger (peace and blessings of
Allaah be upon him): "Myslave does not draw near to Me with anything
more loved by Me than the religious duties I have enjoined on him."
Then He says: "And My slave continues to draw near to Me with
supererogatory works sothat I shall love him." Outward physical acts
are not valid and acceptable unless they are accompanied by
appropriate actions of the heart, because the heart is like the king
andthe physical faculties arelike his troops. If the king is evil his
troops will also be evil. Hence the Prophet (peace and blessings of
Allaah be upon him) said: "In the body there is a piece of flesh: if
it is sound the whole body will be sound and if it is corruptthen the
whole body willbe corrupt." Similarly the (hidden) actions of the
heart inevitably affect the (visible) physical actions. So precedence
must be given to that which is more obligatory, whether it is called
inward or outward. Perhaps things that are called inward may be more
obligatory, such as refraining from destructive envy and arrogance,
for that is more essential than observing naafil fasts. Oracts that
are described as outward or physical may be better, such as qiyaam
al-layl (praying at night), which is betterthan simply giving up some
thoughts that may cross one's mind such as (non-destructive) jealousy,
etc. Inward andoutward deeds support one another, and prayer keeps one
from doing evil actions and generates fear of Allaah, and has other
important effects. It (prayer) is the best of good deeds and charity.
And Allaah knows best.
Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him), Majmoo'
al-Fataawa, 6/381
So there is no separationbetween correcting what is inward and
correcting what is outward or physical.
The outward acts of worship which a person performs with his physical
faculties – if he does them for the sake of Allaah – will undoubtedly
have an effect on his inward nature.
For example, the Prophet (peace and blessings of Allaah be upon him)
said: "Shall I not tell you of something that will take away the evil
of the heart? Fasting three daysof each month." (Narrated by
al-Nasaa'i, 2386; classed as saheeh by al-Albaani in Saheeh
al-Nasaa'i, 2249). The evil of the heart refers torancour, hatred and
destructive envy.
One of the most important remedies for diseases of the heart is to
study and ponder the texts which include warnings to the one who
leaves these diseases to fester in his heart, such as the hadeeth in
which the Prophet (peace and blessings of Allaah be upon him) said:
"No one will enter Paradise who has an atom's-weight of arrogance in
his heart." (Narrated by Muslim, 91).
And the hadeeth according to which Hell will say, "My share is the
arrogant." (Narrated by al-Bukhaari, 4850; Muslim, 2846)
And the hadeeth: "On the Day of Resurrection the arrogant will be
gathered like ants in the form of men." (Narrated by al-Tirmidhi,
2492; classed as hasan by al-Albaani in Saheeh al-Tirmidhi, 2025).
And the Prophet (peace and blessings of Allaah be upon him) said: "The
disease of the nations who came before you has started to spread among
you: destructive envy and hatred. These are the shavers. I do not mean
that they shave hair but they shave away religious commitment. By the
One in Whose hand is my soul, you will not enter Paradise until you
believe, and you will notbelieve until you love one another. Shall I
not tell you of something which if you do it, you will love one
another. Spread (the greeting of) salaam amongst yourselves."
(Narrated by al-Tirmidhi, 2510; classed as hasan by al-Albaani in
Saheeh al-Tirmidhi, 2038).
Whoever ponders with true insight such warnings about the diseases of
the heart willundoubtedly strive to cleanse his heart thereof, and
will seek help in doing so by doing outward physical acts, praying to
his Lord to cleanse his heart of hatred, destructive envy,rancour and
so on, as Allaah says, describing the prayer of the believers:
"and put not in our hearts any hatred against those who have believed"
[al-Hashr 59:10 – interpretation of the meaning]
And Allaah knows best. May Allaah send blessings upon our Prophet Muhammad.