Dought & clear - , What is narrated about the virtue of sponsoring orphans, and the relationship of the orphan girl to the one who adopted her after she reaches puberty

If a man adopts an orphan girl, and she has no ties of kinship with
him, is this girl obliged when she grows up to observe hijab in front
of this man? What are the matters that he must bear in mind with
regard to the issue of adoption, taking into consideration the fact
that he did not give her his name? All the man wants is to attain the
reward mentioned in the hadeeth of the Prophet (blessings and peace of
Allah be upon him): "Whoever raise two girls until they reachpuberty
and get married, he and I will be like these two on the Day of
Resurrection" andhe held together two of his fingers. Narrated by
Muslim and at-Tirmidhi.
Praise be to Allaah.
Firstly:
The Messenger of Allah (blessings and peace of Allah be upon him)
said: "Whoever takes care of two girls until they reachpuberty, he and
I will come like this on the Dayof Resurrection" – and he held his two
fingers together.
Narrated by Muslim (2631). According to a report narrated by
at-Tirmidhi (1914): "Whoever takes care of two girls, he and I will
enter Paradise like thesetwo" and he gestured with his two fingers.
The commentators interpreted the virtue mentioned in the two hadeeths
as referring to daughters and sisters. Imam Muslim narrated inthe
previous hadeeth, "Whoever takes care of two girls…" in the chapter on
"The virtue of treating daughters with kindness." And Imam at-Tirmidhi
narrated it in the chapter on "What was narrated about spending on
daughters and sisters."
The one who takes care of his daughters and sisters properly will
attain the virtue mentioned in these hadeeths, which is beingwith the
Prophet (blessings and peace of Allah be upon him) in Paradise.
But with regard to the virtue of sponsoring orphans and the great
reward for that, Muslim (2983) narrated that AbuHurayrah (may Allah be
pleased with him) said: The Messenger of Allah (blessings and peace of
Allah be upon him) said: "The one who sponsors an orphan, whether it
is a relative of his or not, he and I will be like these two in
Paradise," and Maalik pointed with his forefinger and middle finger.
An-Nawawi (may Allah have mercy on him) said:With regard to the words
"whether it is a relative of his or not", the one who is a relativeof
his is one who is related to him such as his grandfather,
mother,grandmother, brother, sister, paternal uncle, maternal uncle,
maternalaunt, paternal aunt, and other relatives. And the one who is
not a relativeis one with whom he hasno blood ties. End quote from
Sharh Muslim by an-Nawawi.
It is proven in at-Tirmidhi (1918) that Sahl ibn Sa'd (may Allah be
pleased with him) said: The Messenger of Allah (blessings and peace of
Allah be upon him) said: "I and the onewho sponsors an orphanwill be
in Paradise like these two," and he gestured with his two fingers,
meaning the forefinger and the middle finger. Classed as saheeh by
Shaykh al-Albaani in Saheeh Sunan at-Tirmidhi.
Secondly:
In the answer to question no. 126003 we discussed the issue of
adoption and said that itis of two types, permissible and forbidden.
With regard to the permissible type, it means looking after the orphan
and taking care of his affairs, without attributing the orphan to the
one who adopts.
In that answer, we also stated that when the girlreaches puberty, her
sponsor is regarded as a non-mahram to her, so itis not permissible
for herto uncover her face in front of him or to be alone with him,
but she may uphold ties with him by greeting him andasking him how he
is, in return for his kindness and generosity towards her when she was
small.
It says in Fataawa al-Lajnah ad-Daa'imah: Itis not permissible for you
to stay with this man who adopted you, and it is not permissible for
you to uncover your face in front of him, because he is a non-mahram
to you and adoption does not meanthat you are related. … But there is
nothing wrong with greeting him verbally without shaking hands,
praying for him and thanking him for his kindness.
End quote from Fataawa al-Lajnah ad-Daa'imah, 20/363-364
And Allah knows best.