Thankfulness Prayer

Thankfulness Prayer or Al-Shukr Prayer (Arabic: صَلاةُ الشُّکْر) is a recommended prayer performed to thank and express gratitude to God. Thankfulness Prayer does not have a special form, time or conditions and is performed as a normal "two-rak'a prayer". Like other recommended prayers, it can be performed while sitting, standing, walking, inside a vehicle, etc. But, it is better to be performed while standing.

However, a Thankfulness Prayer is narrated from Imam al-Sadiq (a) with a special instruction as below:

When you are bestowed a divine blessing, perform two rak'as of prayer. In the first rak'a, recite Qur'an 1 (Sura al-Fatiha) and then Qur'an 112 (Sura al-Ikhlas) and in the second rak'a, recite Qur'an 1 first and then recite Qur'an 109 (Sura al-Kafirun). In ruku' and sajda of the first rak'a say:
All praise, thankfulness and gratitude belong to Allah	اَلْحَمْدُ لِلهِ شُکْراً شُکْراً وَ حَمْداً
and, in ruku' and sajda of the second rak'a, say:
All praise belongs to God who fulfilled my du'a and met my request.	اَلْحَمْدُ لِلهِ الَّذِی اسْتَجَابَ دُعَائِی وَ أَعْطَانِی مَسْأَلَتِی
In some sources, it is instructed to recite the following du'a in ruku' and sajda of both rak'as
All praise belongs to Allah, gratitude and praise belong to Allah	اَلحَمدُ لِلهِ شُکراً شُکراً لله وَ حَمداً
and to recite this du'a after the end of the prayer:
All praise belongs to the Allah Who fulfilled my need and met my request.	اَلحمدُ للهِ الَّذی قَضا حَاجَتی وَ أعطانی مَسأَلَتی

Also, it is recommended to recite du'a of Imam al-Sajjad (a) which is mentioned in al-Sahifat al-Sajjadiyya after the Thankfulness Prayer.

In addition to this prayer mentioned in Shi'a sources, Sunnis too have transmitted a prayer from the Prophet (s), reporting that after the conquest of Mecca in order to thank God for the victory, the Prophet (s) performed four "two-rak'a prayers" as a Thankfulness Prayer. Thus, some of the companions followed him (a) and performed this prayer after their victories.