Seeking beneficial Knowledge

The Prophet  used to say
after the Fajr prayer: "O Allaah! I ask you for the Knowledge which is beneficial and sustenance which
is good and deeds which are acceptable (righteous)".
"Allahumma, innee as-aluka 'ilmaan naafiyaan wa rizKan tae'eban wa Amalan
mutakabbalan."
[Sahih Ibn Majah 1/152]

Seeking Beneficial Knowledge
From "The Concise Legacy" of Shaikhul-Islam Ibn
Taymiyyah
Published by JIMAS
Abul `Aasim al-Qaasim bin Yoosuf bin Muhammad at-Tajeebee as-Sabtee
al-Maghribee said:

I requested our leader, the shaykh, faqeeh, imaam, respected scholar,
vanguard of the predecessors, leader of the later generations, reviver of
the Deen, expresser of rare and wonderful ideas with great eloquence and
literacy, the most knowledgeable person I have met in the lands of the
East and West, Taqi ud-Deen Abul-`Abbaas Ahmad bin Taymiyyah (may Allaah
enable us to continue benefiting from him):

[some questions deleted...]

To point me towards those books which I may rely upon regarding
knowledge of hadeeth, and other sciences of the sharee`ah....

Shaykhul-Islam Ibn Taymiyyah answered:

All praise be to Allaah, Lord of the Worlds.

As for which books one may depend on for the different branches of
knowledge, then this is a vast topic, and again, the answer to this varies
according to people's backgrounds in different lands. This is because in
each land, one field of learning or way or mode of thinking may be easier
than another, but the source of all good and blessings is that one
seeks help from Allaah in acquiring knowledge inherited from the Prophet
, because that is what is truly fit
to be named knowledge. Anything else is either not knowledge at all even
though people call it so, or it is knowledge which is not beneficial, or
it is beneficial knowledge, in which case it is necessarily true that
there  exists in the inheritance of Muhammad  that which replaces it, being similar to it or better than
it.

Thus the person's effort should be to understand the purposes of the
Messenger , in his commands,
prohibitions and his various other sayings. When the heart is contended
that something is indeed as the Messenger , intended, then he should not waver from it as far as
possible, whether it is regarding his duties to Allaah or to the
people. In all branches of knowledge, he should strive to hold firmly to
principles narrated from the Prophet ; if he is in doubt regarding any matter about which the
people of knowledge have differed, then he should supplicate to
Allaah with the du`aa which appears in Saheeh Muslim narrated by
`Aa'ishah , that when the Messenger
, stood for the night prayer, he
would say,

"O Allaah! Lord of Jibreel, Meekaa'eel and Israafeel, Originator of the
Heavens and the Earth, Knower of the Unseen and the Present! You judge
among your slaves regarding what they have differed in. Guide me to the
truth regarding that in which they have differed, for truly, You do guide
whomsoever You wish to a path that is straight."

This is because Allaah the Exalted has said, as narrated by His Messenger
 from Him,

"O My slaves, all of you are astray except those that I have guided, so
seek guidance of Me and I shall guide you." [Hadith Qudsi - Sahih Muslim]

As for a description of good books and compilations: people will have
heard from me what Allaah has made easy on other occasions. I will say
this much now, that out of all the compiled books which have been divided
into chapters, there is none more beneficial than the Saheeh of Muhammad
bin Ismaa`eel al-Bukhaaree. However, this alone is not enough to cover all
the major principles of knowledge, nor can it fulfill all the objectives
of one who seeks to dive deep into the various branches of knowledge. It
is imperative that other ahaadeeth, as well as the words of the people of
understanding and the people of knowledge of different specialised fields
be known, for the Ummah has progressed tremendously in all fields of
learning. He whose heart Allaah enlightens He guides him through what
reaches him; but he whose heart Allaah blinds, many books only increase
him in confusion and misguidance, as the Prophet , said to Ibn Labeed al-Ansaari,

"Did the Jews and Christians not have the Tauraat and the Injeel? So what
benefit did these bring them?" [al-Bukhaaree in Khalq Af`aal al-`Ibaad,
an-Nasaa'ee, Ahmad, al-Haakim, ibn Hibbaan, Saheeh]

So we ask Allaah Almighty that He sustains us with guidance and firmness,
instills in our hearts our correct direction, protects us from the
mischief of our own selves, that He does not allow our hearts to deviate
after giving us guidance and that He bestows on us Mercy from Him, for He
is the Most Generous.

All Praise be to Allaah, Lord of the Worlds, and His Blessings be on the
most noble of the messengers.