This thikr is to be said in the prayer
9-12-2015 | IslamWeb
Question:
Assalaamu alaykum. The two hadiths below confuse me. I was wondering if what the prophet, sallallaahu 'alayhi wa sallam, recommended Umm Sulaim with is to be said within the prayer after the tashahhud, or at any time, or both? Here are the hadiths: Umm Sulaim came to the Prophet, sallallaahu 'alayhi wa sallam, and said, “O Messenger of Allaah, sallallaahu 'alayhi wa sallam, teach me some words that I may supplicate with during my prayer." He said, “Glorify Allaah (by saying SubhanAllaah) ten times, and praise Him (by saying Alhamdulilaah) ten times, and magnify Him (by saying Allaahu Akbar) ten times, then ask Him for what you need; He will say, ‘Yes, yes.’” [Sunan An-Nasa'i] Umm Sulaym (may God be pleased with her) came to the Prophet and said, “O Messenger of Allaah, teach me some words that I can supplicate with.” He responded, “Glorify Allaah (say subhanAllaah) ten times, and praise Allaah (say alhamdulillaah) ten times, and magnify Allaah (say Allaahu akbar) ten times and then ask for your need, surely Allaah will say, ‘Surely, I have done it. Surely, I have done it.’” (Ahmad) Assalaamu alaykum.
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad 
is His slave and Messenger.
The hadeeth to which the questioner refers was cited in Imaam Ahmad’s Musnad on the authority of Anas ibn Maalik 
and reads as follows: “Umm Sulaym came to the Prophet and said, ‘O Messenger of Allaah, teach me some words that I may supplicate with.’ He said, ‘Glorify Allaah (by saying Subhaan Allaah) ten times, and praise Him (by saying Alhamdulillaah) ten times, and magnify Him (by saying Allaahu Akbar) ten times, then ask Him for what you need; He will say, ‘Surely, I have done it; surely, I have done it (i.e. granted you your need).’’”
Shaykh Shu'ayb Al-Arnaa’oot 
declared its chain of narration hasan (good). It did not contain the phrase “in my prayer.” Rather, the version of the hadeeth cited by At-Tirmithi, An-Nasaa’i, and Ibn Khuzaymah 
reads - and this very wording is An-Nasaa’i’s and Ibn Khuzaymah’s: "She said, ‘Teach me some words that I may say in my prayer.’” Al-Albaani declared the chain of narration of At-Tirmithi’s version hasan and declared the versions of other reporters as Saheeh li Ghayrih (sound because of corroborating evidence, i.e. due to the availability of other good chains of narration with the same content) in his compilation As-Silsilah As-Saheehah under the number 2008 and in Saheeh Al-Jaamiʻ under the number 679. In his book As-Silsilaah As-Saheehah, he stated, while investigating the hadeeth narrated by Umm Raafiʻ and not Umm Sulaym under the number 3338, that it is most likely that this thikr is to be to recited in the prayer after Takbeeratul Ihraam. The hadeeth narrated by Umm Raafiʻ reads:
“O Umm Raafiʻ! If you rise for the prayer, recite tasbeeh ten times, tahleel ten times, tahmeed ten times, takbeer ten times, and seek His forgiveness ten times; when you recite tasbeeh ten times, Allaah would say, ‘This is for Me!’ When you recite tahleel, He would say, ‘This is for Me!’ When you recite tahmeed, He would say, ‘This is for Me!’ When you recite takbeer, He would say, ‘This is for Me!’ When you seek forgiveness, He would say, ‘You have been forgiven!’” This hadeeth was cited by Ibn As-Sunni in his book ʻAmal Al-Yawm wal-Laylah.
Al-Albaani commented:
“The authentically reported practice of the Prophet indicates that the supplications mentioned in the hadeeth are to be recited in the prayer. It has been narrated on the authority of 'Aa’ishah 
that the Prophet used to recite the following in the beginning of the night prayers (after Takbeeratul Ihraam): He used to recite takbeer ten times, tahmeed ten times, tasbeeh ten times, tahleel ten times, and then seek forgiveness ten times...” [Abu Daawood and others]
Based on the information above, the thikr (remembrance of Allaah) about which you are asking is recited in the prayer.
Allaah knows best.