In a general look at our hadiths, they can be divided into two groups; some are reliable and can be referred to as sahih (a term literally meaning “correct” that refers to an authentic hadith), while others aren’t reliable and are called tha’if (literally meaning “weak”) and majhul (literally means “unknown”).

In order to be able to rely on a hadith and act according to it, fiqh and Islamic experts are required to analyze its sanad (chain of narrators) to see if it is an authentic one or not and in other words, see if its narrators are qualified for narrating or not. After making sure that a hadith’s sanad is an authentic one, they pay attention to and make use of it, citing and relying on it in their jurisprudential activities. But if a hadith’s sanad is unknown or a weak one, or one that doesn’t name all of the narrators till the imam, it can no longer be relied on and made use of.

The hadith that has been asked of has been cited in Biharul-Anwar, and its main source is the book of “Manaqibu Ale-Abi-Taleb”, work of Ibn Shahr Ashub. The text of the hadith is as follows:

الباقر والصادق (ع) انه کان النبی (ص) لاینام حتی یقبل عرض وجه فاطمة و یضع وجهه بین ثدیی فاطمة ویدعولها، وفی روایة: حتی یقبل عرض وجنة فاطمة او بین ثدییها.[1]

(Imam Baqir and Imam Sadiq [as] said that the Prophet [pbuh] wouldn’t sleep until he would kiss the middle of Lady Fatimah’s face and place his face between her breasts and pray for her.)

It has also been narrated that he wouldn’t sleep until he would kiss the middle or the side of her cheek or in between her breasts.)

Ibn Shahr Ashub, born in 588 (lunar calendar) and author of the book “Manaqib”, says in the introduction of his book: “I have narrated these hadiths either from a group of my companions (Shias), or from the Sunnis.” He then goes on to mention one general sanad for all of the books that he has used for narrating these hadiths (regardless of whether they are Sunni or Shia books).

As for the disputed hadith, he has not mentioned any specific source that it has been obtained from, and no other sanad for it, making it a mursal (a hadith whose sanad hasn’t been completely mentioned and isn’t known) one. Therefore, first of all, it isn’t a reliable hadith, and secondly, if we were to assume that hadiths of this type were reliable, paying attention to some key points can solve any possible questions that might come up:

1- The holy Prophet (pbuh) and the Ahlul-Bayt, are of a very high rank and possess some unique spiritual characteristics that make them incomparable with others. For instance, the holy Quran has spoken of their extreme purity in the verse known as “The verse of purification” (انما یرید الله لیذهب عنکم الرجس اهل البیت و یطهرکم تطهیراً).[2] (Allah [swt] only wants to remove all impurity and sin from you, Oh Ahlul-Bayt, and thoroughly purify you.)

Using the term “انما”, which is used to show that something exclusively belongs to a certain case or instance, is proof that this blessing is one that has solely been granted to the Prophet’s household, thus with the help of Allah and according to his desire, and with the help of their own righteous deeds, the infallibles never get close to sins, although they are able to do so.

The term “رجس” is used for any impurity, regardless of what type; whether it is an impurity that human nature considers impure, or one that religion considers impure, or even both. The term “تطهیر” means purification and in this verse, is an emphasis on all impurities being removed from the Ahlul-Bayt.

According to all Islamic scholars and commentators of the Quran, “اهل البیت” refers to the household of the Prophet (pbuh), and many hadiths in both Shia and Sunni sources assert that what is meant by the household of the Prophet (pbuh) are five individuals: Prophet Muhammad (pbuh), Ali (as), Fatimah (as), Hasan and Husain (as), who are also known as “The Noble Five” or “The Companions of the Cape”.

“The Verse of Purification” is concrete evidence on the infallibility of the Prophet (pbuh) and his household (as), because all sins are a form of impurity and according to the verse, they have been purified of all impurity.[3]

In the very rich and valuable supplication of “Ziyaratu Jami’atil-Kabirah” we read: عصمکم الله من الزلل و آمنکم من الفتن وطهرکم من الدنس و اذهب عنکم الرجس و طهرکم تطهیراً which means that Allah protected you (The Ahlul-Bayt) from wrongdoing, saved you from corruption, cleaned you from filth (immorality), removed all impurity from you and thoroughly purified you.[4]

2- Among all of the daughters of the Prophet (pbuh), Lady Fatimah (as) is above all and an exceptional one, and the beginning of her creation is an extraordinary one.

Here, we will draw your attention to a hadith that Ibn Shahr Ashub narrates, but this time with several sanads for it (and not like the one that was mentioned in the question above which had no sanad):

Abu ‘Ubaidah Khadda’ and others report that Imam Sadiq (as) said that the Prophet (pbuh) would kiss Lady Fatimah (as) frequently. Some of his wives were troubled by this act and objected to it. The holy Prophet (pbuh) replied: When I was raised to the skies, Gabriel took my hand and led me to paradise. There, I was given a date which I ate (in another tradition it has been stated that he was given an apple). The fruit turned into a sperm seed in my back and once I returned to earth I slept with Khadijah and she became pregnant with Fatimah (as). Therefore she is a heavenly woman that is living among normal humans and every time I miss and long for the fragrance of paradise, I smell my daughter.[5]

Therefore, the relationship between the Prophet (pbuh) and his daughter is a deep one and his love and fondness towards her is manifest to all.

3- One can easily see a warm and sincere relationship between the members of normal and sound families which lacks any form of lust and passion in all cases, whether it is them looking at each other, shaking hands or even kissing each other. For example, when one's mother, sister or daughter come back from a pilgrimage trip (for instance Hajj), he kisses them, because they have returned from a sacred place.  Such forms of showing love, care and happiness are all solely for the spiritual blessings they carry, nothing more.

Sometimes, Allah (swt) grants a beautiful and polite child to a couple. When they repeatedly kiss him and show him affection, it shows that there is a very tight relationship between them and no one scolds them for such acts.

4- It seems that the main cause for such a question is that the person who is questioning, thinks that the Prophet (pbuh) would kiss Lady Fatimah's chest while it had no covering while such a perception is totally incorrect. That is because observing such borders in very normal people is ordinary, and crossing these red lines is considered breaking family and social moral values and codes. Thus, how can one even think about high characters such as the infallibles committing such acts? In addition to the fact that Lady Fatimah (as) was a mere child during the time she lived with the Prophet (pbuh) and as soon as she reached the age of 9, she got married with Imam Ali (as).

Therefore, when such forms of affection and love between family members are completely normal and accepted by all, they are also acceptable by the infallibles.

Indeed, there are important reasons behind why they sometimes express their love for certain family members (such as to show others how important that person is for them in order for others to also respect them) and in this case, these types of hadiths that are sometimes questioned about, have no problem and their interpretation is clear.