What is the ruling on giving two adhaans and two iqaamahs when joining prayers?

The scholars differed concerning giving two adhaans and two
iqaamahs when joining prayers. The correct view is that one adhaan should be
given for both prayers, then two iqaamahs, one iqaamah for each prayer. 

This is the view of the Hanafis and Hanbalis, and it the
favoured view of the Shaafa’is, and it is the view of some of the Maalikis.
 

See al-Mawsoo’ah al-Fiqhiyyah, 2/370 

The evidence for that is
what it is proven that the Prophet (peace and blessings of Allaah be
upon him) did during the Farewell Pilgrimage, when he prayed Zuhr and ‘Asr
in ‘Arafah, joining them at the time of the earlier prayer, with one adhaan
and two iqaamahs, and he prayed Maghrib and ‘Isha’ in Muzdalifah, joining
them at the time of the later prayer, also with one adhaan and two
iqaamahs. 

It was narrated that Jaabir ibn ‘Abd-Allaah (may Allaah be
pleased with him) said, describing the hajj of the Prophet (peace and
blessings of Allaah be upon him): 

Then he gave the adhaan and the iqaamah, then prayed Zuhr,
then he gave the iqaamah and prayed ‘Asr, and he did not offer any other
prayer between them… Then he came to Muzdalifah where he prayed Maghrib and
‘Isha’ with one adhaan and two iqaamahs. Narrated by Muslim, 1218. 

The scholars of the Standing Committee were asked: 

Some of the fuqaha’ say that Maghrib and ‘Isha may be joined
together with two adhaans in the case of rain. What is the ruling on that? 

They replied: 

The Sunnah is to join
Maghrib and ‘Isha’ with one adhaan and two iqaamahs, if there is a
justification for doing so, such as travelling, sickness, and rain when one
is not travelling. This is what is clearly indicated by the saheeh Sunnah,
based on the actions of the Prophet (peace and blessings of Allaah be
upon him). End quote. 

Fataawa al-Lajnah al-Daa’imah li’l-Buhooth al-‘Ilmiyyah
wa’l-Ifta’, 8/142 

Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allaah have
mercy on him) said: 

If a person joins prayers, he should say the adhaan for the
first one, and the iqaamah for each obligatory prayer. This applies if he is
not in a city; if he is in a city then the adhaan of the city is sufficient,
and he should say the iqaamah for each obligatory prayer.

 The evidence for that is the hadeeth narrated in Saheeh
Muslim from Jaabir, according to which the Prophet (peace and
blessings of Allaah be upon him) gave the adhaan in ‘Arafah, then he said
the iqaamah and prayed Zuhr, then he said the iqaamah and prayed ‘Asr, and
he did likewise in Muzdalifah when he gave the adhaan and iqaamah and prayed
Maghrib, then he said the iqaamah and prayed ‘Isha’. End quote. 

Al-Sharh al-Mumti’, 2/78, 79 

With regard to the ruling on the adhaan and iqaamah, they are
fard kifaayah (a communal obligation) and it is sufficient for a group if
one of their number says the adhaan and iqaamah. It is not required of each
person in the group. We have quoted above the view of Shaykh Ibn ‘Uthaymeen
(may Allaah have mercy on him) who said that if they are in a city in which
the muezzins in the mosque have already given the adhaan, that is sufficient
for them and they should say the iqaamah for each prayer. 

Shaykh Muhammad ibn Saalih al-‘Uthaymeen (may Allaah have
mercy on him) said: 

The evidence that they – the adhaan and iqaamah – are
obligatory is the fact that the Prophet (peace and blessings of Allaah
be upon him) enjoined them in a number of ahaadeeth, and he always said them
whether he was travelling or not. And in most cases it cannot be known
whether the time for prayer has come without them and because they serve a
purpose, as they are two of the outward symbols of Islam. 

They are obligatory whether one is travelling or not. The
evidence for that is the fact that the Prophet (peace and blessings of
Allaah be upon him) said to Maalik ibn Huwayrith and his companions: “When
the time for prayer comes, let one of you give the adhaan to you.” Agreed
upon. They had come to the Messenger of Allaah (peace and blessings of
Allaah be upon him) and were now travelling back to their families, and the
Messenger (peace and blessings of Allaah be upon him) instructed that
one of them should give the adhaan for them. And the Prophet (peace and
blessings of Allaah be upon him) did not neglect the adhaan or iqaamah
whether he was travelling or not. When he was travelling he would tell
Bilaal to give the adhaan. 

The correct view is that it is obligatory for those who are
travelling and those who are not. They should give the adhaan for each of
the five obligatory prayers, so long as prayers are not being joined. If
prayers are being joined then one adhaan is sufficient for two prayers, but
it is essential to say the iqaamah for each prayer. 

Al-Sharh al-Mumti’, 2/42-46 

And Allaah knows best.