He does not pray in congregation because of his work

Prayer in
congregation is obligatory at all times, because Allaah says (interpretation
of the meaning): 

“When you
(O Messenger Muhammad) are among them, and lead them in As‑Salaah (the
prayer), let one party of them stand up [in Salaah (prayer)] with you taking
their arms with them; when they finish their prostrations, let them take
their positions in the rear”

[al-Nisa’
4:102]

Allaah has
enjoined prayer in congregation at times of war, so how about at times of
peace? 

Al-Bukhaari
(608) and Muslim (1040) narrated that the Prophet (peace and blessings
of Allaah be upon him) said: “I was thinking of ordering that firewood be
gathered, then I would order that the call to prayer be given, then I would
order a man to lead the prayer, then I would go to men who do not attend the
prayer and I would burn their houses down around them.” In Saheeh Muslim
(1044) it says: A blind man came to the Prophet (peace and blessings of
Allaah be upon him) and said: “O Messenger of Allaah, I do not have a guide
to bring me to the mosque.” He asked the Messenger of Allaah (peace and
blessings of Allaah be upon him) to grant him a concession allowing him to
pray in his house, and he granted him that concession, but when he turned to
leave he said: “Can you hear the call to prayer?” He said: “Yes.” He said:
Then answer it.” So the Muslim should regularly pray in congregation at all
times, and not let any worldly distractions keep him away from that. 

Allaah says
(interpretation of the meaning): 

“O you
who believe! Let not your properties or your children divert you from the
remembrance of Allaah. And whosoever does that, then they are the losers”

[al-Munaafiqoon 63:9]

You should
advise your father and remind him of this saheeh evidence, with wisdom and
beautiful preaching. 

This ruling
applies to offering the five daily prayers in congregation. With regard to
Taraweeh, the matter is easier than that. It is permissible for a Muslim to
pray Taraweeh at home, although it is better to pray it in congregation in
the mosque. 

It is not
permissible for a Muslim to devote himself to worldly work at the expense of
his worship and prayer. Allaah has described the believers as those who do
not let their trade and selling distract them from the remembrance of Allaah
and establishing prayer. Allaah says (interpretation of the meaning): 

“In
houses (mosques) which Allaah has ordered to be raised (to be cleaned, and
to be honoured), in them His Name is remembered [i.e. Adhaan, Iqaamah,
Salaat (prayers), invocations, recitation of the Qur’aan]. Therein glorify
Him (Allaah) in the mornings and in the afternoons or the evenings,

37. Men
whom neither trade nor sale (business) diverts from the remembrance of
Allaah (with heart and tongue) nor from performing As‑Salaat
(Iqaamat‑as‑Salaat) nor from giving the Zakaah. They fear a Day when hearts
and eyes will be overturned (out of the horror of the torment of the Day of
Resurrection).

38. That
Allaah may reward them according to the best of their deeds, and add even
more for them out of His Grace. And Allaah provides without measure to whom
He wills”

[al-Noor
24:36-38]

This passage
ends with the words “And Allaah provides without measure to whom He wills”,
which hints to the one who spends his time in trade and work at the expense
of his obedience to his Lord, that provision is in the hand of Allaah and He
provides without measure to whom He wills. The Prophet (peace and
blessings of Allaah be upon him) explained that when he said: “O people,
fear Allaah and be moderate in seeking a living, for no soul will die until
it has received all its provision, even if it is slow in coming. So fear
Allaah and be moderate in seeking provision; take that which is permissible
and leave that which is forbidden.” Narrated by Ibn Maajah, 2144, from the
hadeeth of Jaabir ibn ‘Abd-Allaah (may Allaah be pleased with him); classed
as saheeh by Shaykh al-Albaani in Saheeh al-Targheeb (1698). 

There is no
reason why you should not do what you can to earn a living, but the Muslim
should not go to extremes with work and devote all his time to it at the
expense of his worship, health and raising his children. He should create a
balance between everything. 

We hope that
your father will study what we have said and think about it properly. We ask
Allaah to guide him to the best of words, deeds and attitudes, and to bless
him with a goodly and blessed provision. 

And Allaah
knows best.