It is absolutely necessary for Muslims to be careful about time.
The Muslim is required to utilize and invest his time in what benefits him in
this world and the Hereafter. In this regard, he can follow the good example set
by the Righteous Salaf. They were so careful that in less than a century they
were able to make radical changes in the societies into which they introduced
Islam.
The Righteous Salaf made sure that no time, however short it was,
passed without doing something useful, such as acquiring useful knowledge, doing
good deeds, helping other Muslims and serving or advising the Ummah (nation).
Remarking Imam Hammad Ibn-Salama Al-Basry's [a grammarian] meticulous care for
time, Musa Ibn-Ismaeel said, "It is unbelievable! I have never seen Hammad
laugh at all. He was always busy explaining the Hadith, praying, reading or
praising the Lord. This is how he spent his day. Abdurrahman Al-Mahdi
[Abdurrahman Ibn-Mahdi Ibn-Hassan Ibn-Abdurrahman, a critic and an able reciter;
he was considered a good model for knowledge and work. See: Shamsuddeen
Adh-Dhahabi, ”Biographies of Noble Scholars”, 9/192-193.] said: "If you were to
tell Hammad, 'You are going to die tomorrow', there would be nothing he could
add to what he is already doing." [Abu-Hajjaj Yusuf Al-Mizzi, “Tahdheeb Al-Kamal
fi Asma' Arrijal”, in Arabic, investigated by B. A. Ma'ruf, 1992, Vol. 7, p.
265.]
Regretting the time he spent eating, Shumait Ibn-Ajlan [Abu-Naeem
Al-Asbahani, “Hilyatul-Awliya'wa Tabaqat Al-Asfiya'“ (The Pious Friends'
Ornaments and Classes of the Pure), in Arabic, investigated by Mustafa Abdul-Qadir
Ata, 1418, 3/149] said, "By Allah, the time I hate most is that which I spend
eating." How conscious of time! [Ibid, 3509, 3/151]
Once a wise man said, "If you spend one day on other than carrying
out justice, performing obligatory worship, achieving some gain, praising the
Lord, establishing something good or acquiring knowledge, you have been
ungrateful to your day and have wronged yourself." [Abdurra`uf Al-Minawi, “Faidh
Al-Qadeer bi Sharh Al-Jami` Assagheer”, 6/288]