Is following da’eef hadeeths regarded as shirk?

It cannot be said that acting upon weak (da’eef) hadeeths
is regarded as shirk, because the hadeeths were narrated via chains of
transmission (isnaads) and the scholars researched those chains. In many
cases they found a man in the chain who was described as having a weak
memory, but that does not necessarily mean that the hadeeth is fabricated,
because we cannot accuse that scholar of telling lies and fabricating; but
he may have made a mistake in transmitting the hadeeth or attributing it
to someone, as happened in the case of many muhaddithoon who were
described as being weak in hadeeth. It is permissible to act upon weak
hadeeths subject to 3 conditions: 

1.That the weakness is not so
severe as to make it likely that the hadeeth is fabricated.

2.That the hadeeth comes under a
general principle, such as virtuous deeds.

3.That one does not believe when
acting upon it that it is proven, so that he will not ascribe to the
Messenger of Allah (blessings and peace of Allah be upon him) something that
he did not do.

With regard to the differences between hadeeths, it may be
due to a mistake on the part of one of the narrators; or it may be because
some hadeeths abrogate others as is also the case with the Book of Allah.
With regard to the idea that there are contradictions between the proven,
saheeh hadeeths, this is not correct and cannot happen, because everything
that has come from Allah, may He be exalted, or from His Messenger
(blessings and peace of Allah be upon him) is free from contradiction,
because Allah says (interpretation of the meaning): “Had it [the Qur’aan]
been from other than Allaah, they would surely, have found therein many a
contradiction” [al-Nisa’ 4:82]. So there are no contradicting verses in
the Qur’aan and there are no contradictions in the proven hadeeths of the
Prophet. 

But if the contradiction involves a da’eef or weak hadeeth,
it does not matter, because we say that it is the mistake of one of the
narrators. Some of the scholars regarded it as permissible to act upon
da’eef hadeeth such as those that speak of virtuous deeds; i.e., these
reports encourage us to do some acts of virtue. But if the weak hadeeth
speaks of rulings, we cannot accept it. Hence Imam Ahmad (may Allah have
mercy on him) said: When we narrate hadeeth concerning halaal and haraam, we
are very strict; but when we narrate reports about acts of virtue, we are
more lenient, because no rulings depend on reports about acts of virtue;
rather they are like the virtue of fasting, jihad, prayer and so on. 

And Allah knows best.