What is meant by amaanah in the verse “Truly, We did offer al-amaanah (the trust) to the heavens and the earth, and the mountains”?

Allah, may He be
exalted, offered obedience to Him and His obligations and limits to the
heavens and the earth and the mountains in such a way that if they did
well they would be rewarded, but if they neglected their duties they would
be punished. They refused to bear it out of fear that they might not do
what was enjoined upon them, but man took it on, and verily he was unjust
(to himself) and ignorant (of its results). 

This is the
explanation of the verse in which Allah, may He be glorified and exalted,
says: “Truly, We did offer al-amaanah (the trust or moral responsibility
or honesty and all the duties which Allah has ordained) to the heavens and
the earth, and the mountains, but they declined to bear it and were afraid
of it (i.e. afraid of Allah’s torment). But man bore it. Verily, he was
unjust (to himself) and ignorant (of its results) [al-Ahzaab 33:72]”. 

The interpretation
of the amaanah (trust) as referring to shar‘i duties is the view of Ibn
‘Abbaas, al-Hasan al-Basri, Mujaahid, Sa‘eed ibn Jubayr, ad-Dahhaak ibn
Muzaahim, Ibn Zayd and most of the commentators. 

See: Tafseer
at-Tabari, 20/336-340; Tafseer Ibn Katheer, 6/488-489;
al-Jaami‘ li Ahkaam al-Qur’an, 14/252-253; Fath al-Qadeer,
4/437. 

Qataadah said: The
amaanah (trust) is the religion, obligatory duties and limits set by Allah. 

It was also said
that what is meant by the amaanah here is whatever people entrust one with. 

Some of them said
that it refers to ghusl in the case of janaabah. 

Zayd ibn Aslam
said: The amaanah is three things: prayer, fasting and ghusl in the case of
janaabah. 

Ibn Katheer (may
Allah have mercy on him) said:

There is no
contradiction between these opinions; rather they are all in harmony and
refer to responsibility and accepting the commands and prohibitions on the
basis of their condition, which is that if they do well they will be
rewarded and if they neglect them they will be punished. Man accepted this
amaanah despite his weakness, ignorance and injustice (to himself), except
those who Allah guides. End quote. 

Tafseer Ibn
Katheer,
6/489 

At-Tabari (may
Allah have mercy on him) said:  

The most correct
of these opinions is that of those who said that what is meant by the
amaanah (trust) here is everything with which one is entrusted with regard
to religious commitment and things entrusted to one by people. That is
because Allah did not specify any particular type of trust when He said, “Truly,
We did offer al-amaanah (the trust)”. End quote. 

Tafseer
at-Tabari,
20/342 

Al-Qurtubi (may
Allah have mercy on him) said: 

The word amaanah
is general in meaning and encompasses all the duties of Islam, according to
the correct opinion. This is the view of the majority. End quote. 

Al-Jaami‘ li
Ahkaam al-Qur’an,
14/252 

As-Sa‘di (may
Allah have mercy on him) said: 

Everything that
Allah has enjoined upon His slave is an amaanah (trust), and the slave must
carry them out in the fullest sense. That also includes things that are
entrusted to one by people, such as wealth, secrets and the like. The
individual must pay attention to both matters and fulfil both trusts.
“Verily! Allah commands that you should render back the
trusts to those, to whom they are due” [an-Nisa’
4:58].
End quote. 

Tafseer
as-Sa‘di,
p. 547 

Ash-Shanqeeti (may
Allah have mercy on him) said: 

In this verse
Allah, may He be glorified and exalted, tells us that He offered the
amaanah, which is the taking on of duties and the consequences of reward or
punishment, to the heavens and the earth and the mountains, but they refused
to bear it and were afraid of it. In other words, they were scared of the
consequences of taking on this trust, lest that lead to the punishment and
wrath of Allah. This offer, refusal and fear happened in a true sense. Allah
created the heavens and the earth and the mountains with a sense of
understanding, the nature of which only Allah knows and we do not know. Thus
they understood when this trust was offered to them, and they refused and
were afraid. End quote. 

Adwa’ al-Bayaan,
36/139 

To sum up: 

The amaanah
(trust) mentioned in this verse, that Allah offered to the heavens and the
earth and the mountains, but they refused to bear it and were afraid of it,
but man took it on, is the Islamic duties, whether that has to do with
duties towards Allah, may He be exalted, or duties towards His slaves. The
one who fulfils his duty towards Allah and towards His slaves will be
rewarded, but the one who neglects his duty towards Allah and towards His
slaves deserves punishment. 

And Allah knows
best.