Praise be to Allah, the Lord of the Worlds.
In general, raising hands in Du`a (Supplication) is a recommended Sunnah, which is indicated by many Hadiths. Some of them were reported by al-Bukhari (May Allah have mercy on him) in his Sahih (Book of Supplications/ Chapter on Raising Hands in Du`a). He has also included them in a special book entitled "Juzu` Rafie al-Yadain." In his books "al-Athkar" and "al-Majmou` Shareh al-Mohathab," An-Nawawi reported a number of Hadiths supporting this Sunnah, which reflects how humbly submissive a Muslim gets when making Du`a to Allah.
Many Hadiths have also indicated this Sunnah.For Example, Abu Huraira reported Allah`s Messenger (PBUH) as saying: "… He then made a mention of a person who travels widely, his hair disheveled and covered with dust. He lifts his hand towards the sky (and thus makes the supplication): "O Lord, O Lord," {Related by Muslim}. Also, Salman Al-Farsi narrated that the Prophet (PBUH) said: “Indeed, Allah, is Hayy, Generous, when a man raises his hands to Him, He feels too shy to return them to him empty and rejected.”{Related by Tirmizi & Abu Dawoud}.
However, Anas bin Malik narrated: "The Prophet (PBUH) never raised his hands for any invocation except for that of Istisqa' and he used to raise them so much that the whiteness of his armpits became visible,"{Related by Bukhari}. Commenting on "except for that of Istisqa'," al-Hafiz Ibn Hajar (May Allah have mercy on him) said, "apparently, raising the hands should be limited to the case of making Du`a for Istisqa`(Salat in which people ask Allah to bring the rain). However, there are other reports proven from the Prophet (PBUH) that there are other instances in which it is permissible to raise the hands when making Du`a."{Fateh al-Bari, 2/517}.In order to get out of this contradiction, Ibn Hajar said that this Hadith (Narrated by Anas) indicates the Prophet`s (PBUH) over-raising of his hands. Therefore, it means that He (PBUH) has never raised his hands so much that the whiteness of his armpits became visible except when He made Du`a for Istisqa`.
The majority of the scholars are also of this view: "It is from Sunnah that he raises his hands when making Du`a-Qunoot-and all other Du`as (Supplications) as indicated by Hadiths. {Moghni al-Mohtaj, 1/370}.
" Narrated Anas bin Malik: Once in the lifetime of the Prophet (PBUH) the people were afflicted with drought (famine). While the Prophet (PBUH) was delivering the Khutba on a Friday, a Bedouin stood up and said, "O, Allah's Messenger (PBUH)! Our possessions are being destroyed and the children are hungry; Please invoke Allah (for rain)". So the Prophet (PBUH) raised his hands. At that time there was not a trace of cloud in the sky. By Him in Whose Hands my soul is as soon as he lowered his hands, clouds gathered like mountains, and before he got down from the pulpit, I saw the rain falling on the beard of the Prophet. {Related by Bukhari & Muslim}.This proves that whoever claims that raising the hands should be limited to certain instances is mistaken. "{al-Majmou`, 3/507}.
Al-Imam al-A`yni (May Allah have mercy on him) said, "Raising hands when making Du`a is a Sunnah indicated by many Prophetic narrations; some of which were related by Abu Dawoud in his "Sunnan". For example, Abdullah ibn Abbas narrated: Ikrimah quoted Ibn Abbas as saying: When asking for something you should raise your hands opposite to your shoulders; when asking for forgiveness you should point with one finger; and when making an earnest supplication you should spread out both your hands."{al-Binayah Shareh al-Hidayah, 4/203}.
Al-Imam al-Nafrawi-from the Maliki school-said, "About raising hands in Du`a/supplication outside prayer, is it from Sunnah that he wipes his face with them afterwards or not? Umar bin Al-Khattab [may Allah be pleased with him] narrated: “Whenever the Messenger of Allah would raise his hands in supplication, he would not lower them until he had wiped his face with them.”{al-Fawakeh al-Dawanee, 2/330}.
Al-Imam al-Bahwati-from the Hanabali school-said, "Stretching the hands and raising them to the chest is among the etiquettes of supplication based on the Hadith narrated by Malik ibn Yasar as-Sakuni, al-Awfi: The Prophet (PBUH) said: When you make requests to Allah, do so with the palms of your hands, and not backs, upwards."{Khash-shaaf al-Khinaa`, 1/368}.
Among the instances in which there was disagreement about raising hands in supplication is when the Imam offers supplication at the end of the second part of the Friday sermon. This indicated by the following Hadith related by Muslim: "Umara b. Ruwaiba said he saw Bishr b. Marwan on the pulpit raising his hands and said: Allah, disfigure these hands! I have seen Allah's Messenger (PBUH) gesture no more than this with his hands, and he pointed with his forefinger." An-Nawawi(May Allah have mercy on him) said, "The Sunnah is not to raise the hands when offering supplication at the end of the Friday sermon, and this is the view of Malik, our fellow scholars and other scholars. However, al-Khadi reported that some righteous predecessors and Maliki scholars have permitted that, because the Prophet (PBUH) raised his hands in supplication for Istisqa` at the end of Friday sermon. The first party(Supporters of the view that the Sunnah is not to raise hands when making supplication) replied that the raising of the hands was limited to a certain case."{Shareh al-Nawawi Ala Muslim}.
In conclusion, raising hands when offering supplication is a generally recommended Sunnah indicated by many authentic Hadiths. However, an Imam`s raising his hands in supplication at the end of the second part of the Friday sermon is disagreed on: Imam Malik and the Shafie scholars are of the view that it is impermissible; whereas, some righteous predecessors and Maliki scholars permitted that, and there is no harm in following either view. And Allah knows best.