Sheikh Abdullah bin Abd al-Azhim Khalafi
Doing I'tikaf in the last ten days of Ramadan is a Sunnah that is recommended, with a view to obtaining and seeking Laylat al-Qadr goodness.
Allah Ta'ala says:
إنا أنزلناه في ليلة القدر وما أدراك ما ليلة القدرليلة القدر خير من ألف شهرتنزل الملائكة والروح فيها بإذن ربهم من كل أمر سلام هي حتى مطلع الفجر
"Verily, We have been down (al-Qur-an) on the night of glory. And you know what the Night of Power is? Night of Power is better than a thousand months. At night it drops Angel-Angel and the Angel Gabriel with the permission of his Lord to regulate all affairs. That night (full) welfare until dawn. "[Al-Qadr: 1-5]
It was narrated from 'Aisha radi anhuma, he said that the Prophet sallallaahu' alaihi wa sallam retreat in the last ten days of Ramadan, and he said:
تحروا ليلة القدر في العشر الأواخر من رمضان.
"Seek Laylat al-Qadr in the last ten nights of Ramadan." 
Also narrated from 'Aisha radi anhuma that the Prophet sallallaahu' alaihi wa sallam said:
تحروا ليلة القدر في الوتر من العشر الأواخر من رمضان.
"Seek Laylat al-Qadr in the odd nights of last ten nights of Ramadan." 
Prophet sallallaahu 'alaihi wa sallam has advocated his people to turn on Laylat al-Qadr night. It was narrated from Abu Hurayrah radi anhu, the Prophet sallallaahu 'alaihi wa sallam, he said:
من قام ليلة القدر إيمانا واحتسابا غفر له ما تقدم من ذنبه.
"Anyone who prays night Laylat al-Qadr ingredients of faith and hope for His reward, it will be forgiven the sins of his past." 
I'tikaf should only be done in the mosque, based on the word of God:
ولا تباشروهن وأنتم عاكفون في المساجد
"... (But) they do not interfere in it, while you retreat in the mosque ... "[Al-Baqarah: 187]
Also, because the Prophet sallallaahu 'alaihi wa sallam always retreat inside.
I'tikaf Sunnah for the person to occupy themselves with any form of obedience to God, such as prayer, reading al-Qur'an, saying the rosary, tahmid, tahlil, and Takbir, beristighfar, read the above blessings on the Prophet, praying, studying and others.
And dimakruhkan for them to occupy themselves with things that are not beneficial, whether it be actions or words. So also with restraint to not speak because he considered it as one form of approach to God.
Permissible for people to retreat out of place because there is an urgent need, as well as permissible for them to comb your hair and shave, cut nails and clean the body. I'tikaf someone will be void if he is out of place i'tikafnya without any immediate need and also if he had sexual intercourse.
[Copied from the book Al-Sunnah wal Wajiiz FII Fiqhis Kitaabil Aziiz, author Azhim Shaykh ibn Abdul al-Khalafi Badawai, edition of Indonesia Guide Complete Fiqh, Translation Team Tashfiyah LIPIA - Jakarta, Reader Publishers Ibn Kathir, Ramadan First published in 1428 - September 2007M]
. Saheeh: [Mukhtasar Shahiih al-Bukhari (no. 987)], Shahiih al-Bukhari (Fat-Hul Baari) (IV/259, no. 2020), Sunan at-Tirmidhi (II/144, no. 789).
. Agreed upon: al-Bukhari Shahiih (Fat-Hul Baari IV/259, no. 2017), Muslim Shahiih (II/628, no. 1169).
. Agreed upon: al-Bukhari Shahiih (Fat-Hul Baari IV/255, no. 2014), Muslim Shahiih (I/523, no. 760), Sunan Abu Dawud (IV/146, no. 1359), Sunan an- Nasa-i (IV/157).
. Fiqhus Sunnah (I/404) with the change.