Dought & clear, - [Sifat al-Salaah (description of the prayer)] -> If he catches up with the imam when he is bowing, what should he do?.

If I enter the mosque and the imam is bowing, if I bow with him will
that rak'ah count for me, even though I have not recited al-Faatihah?
Should I say one takbeer or two?.
Praise be to Allaah.
Firstly:
If a person enters the mosque when the imam is bowing, he should bow
with him, and his will have caught up with the rak'ah if he joins the
imam when he is bowing, even if he did not bow fully until after the
imam stands up. Imam Abu Dawood said: I heard Ahmed being asked about
a man who catches up with the imam when he is bowing; he says takbeer
and bows, then the imam stands up. He said: If he placed his hands
firmly on his knees before the imam stood up, then he has caught up
with the rak'ah. End quote.
See:Masaa'il al-Imaam Ahmadby Abu Dawood, p. 35;Haashiyat al-Rawd, by
Ibn Qaasim, 2/275;al-Majmoo, 4/215.
Then he should be at ease in bowing, and rise from bowing, and follow his imam.
Shaykh Ibn Baaz said: If a person catches up with the imam when he is
bowing, that rak'ah counts for him, even if he does not say the
tasbeeh until after the imam has stood up. End quote.
Majmoo' Fataawa Ibn Baaz, 11/245-246
Secondly:
If he catches up with him when he is bowing, then one takbeer is
sufficient, i.e., the opening takbeer counts for the takbeer of bowing
too. That was narrated from Zayd ibn Thaabit, Ibn 'Umar, Sa'eed,
'Ata', al-Hasan and Ibraaheem al-Nakha'i. It was also the view of the
four imams (Abu Haneefah, Maalik, al-Shaafa'i and Ahmad). Abu Dawood
said: I said to Ahmad: What if I catch up with the imam when he is
bowing? He said: One takbeer is sufficient for you. End quote.
Masaa'il al-Imam Ahmad, p. 35
That is because the time for bowing is usually too short to combine
two takbeers, and because it is combining two acts of worship of the
same type in the same place. The intention to bow does not cancel out
the intention to start praying. So the pillar or essential part,
namely the opening takbeer, suffices for the obligatory duty, namely
the takbeer for bowing, just as tawaaf al-ifaadah suffices for the
farewell tawaaf if it is done last of all.
Seeal-Mughni, 2/183;al-Qawaa'idby Ibn Rajab, number 18.
If a person can say two takbeers, one for starting the prayer and one
for bowing, that is better. Abu Dawood said: I said to Ahmad: Is
saying two takbeers dearer to you? He said: If he says two takbeers
there is no dispute on the matter. End quote.
Masaa'il al-Imam Ahmad, p. 35
Shaykh Ibn Baaz was asked: If a person joins the prayer when the imam
is bowing, should he say the takbeers for starting to pray and for
bowing, or say takbeer once and bow?
He replied:
It is better and more on the safe side to say takbeer twice, once for
starting to pray, which is a pillar or essential part of the prayer
which must be done when he is standing, and the second time for bowing
when he starts to bow. If he fears that he may miss the rak'ah, then
the opening takbeer will suffice according to the more correct of the
two scholarly opinions, because they are two acts of worship being
combined at the same time and the greater will suffice for the lesser.
And this rak'ah will count according to the majority of scholars. End
quote.
Majmoo' Fataawa Ibn Baaz, 11/244-245
The one who is joining the prayer has to say the opening takbeer
standing. If he says it whilst leaning forward to bow, it is not
valid.
Al-Nawawi said inal-Majmoo'(4/111):
If a person catches up with the imam when he is bowing, he should say
the opening takbeer standing, then say the takbeer for bowing as he is
leaning forward to bow. If he says some of the opening takbeer when he
is not standing upright, then his prayer does not count as an
obligatory prayer, with no difference of opinion among the scholars on
this point; it also does not count as a naafil prayer, according to
the correct view. End quote.
Seeal-Mughni, 2/130
Shaykh Ibn 'Uthaymeen (may Allaah have mercy on him) said inal-Sharh
al-Mumti'(4/123):
But there is a matter which must be discussed, which is that it is
essential to say the opening takbeer when standing straight, before
leaning forward, because if a person leans forward when saying the
opening takbeer, he will have said the opening takbeer when he was not
standing straight, and the opening takbeer must be said when standing
straight. End quote.
Thirdly:
If he bows with the imam, that rak'ah counts for him even if he does
not recite al-Faatihah. This is the view of the majority and it is the
correct view, in sha Allah, because the Prophet(peace and blessings of
Allaah be upon him) said to Abu Bakrah (may Allaah be pleased with
him), when he came to the Prophet(peace and blessings of Allaah be
upon him) when he was bowing and he bowed before he reached the row.
He mentioned that to the Prophet(peace and blessings of Allaah be upon
him) and he said: "May Allaah make you more keen, but do not do it
again." Narrated by al-Bukhaari, 783.
The point here is that if catching up with bowing did not count as
catching up with the rak'ah with the imam, the Prophet(peace and
blessings of Allaah be upon him) would have told him to make up that
rak'ah in which he did not catch up with the recitation, but no such
thing has been reported from him. This indicates that the one who
catches up with bowing has caught up with the rak'ah.
See Silsilat al-Ahaadeeth al-Saheehah, p. 230.
Al-Shawkaan said: Similarly the Prophet(peace and blessings of Allaah
be upon him) told the one who joins the prayer to do what the imam
does, and it is known that this cannot be done unless he bows with his
imam. If he starts to recite al-Faatihah, he has caught up with the
imam in a state where he is not doing what his imam does, so he has
disobeyed the command to follow the imam. End quote from an essay
quoted by the author of'Awn al-Ma'bood, 3/157
With regard to the evidence for it being obligatory to recite
al-Faatihah in prayer, this is general in meaning and includes the one
who joins the prayer late and the one who does not join the prayer
late. This hadeeth specifically indicates that the obligation to
recite al-Faatihah is waived for the one who catches up with his imam
when he is bowing, so this hadeeth makes an exception from the general
meaning of the other ahaadeeth.
SeeMajmoo' al-Fataawa, 23/290
In the answer to question no. 74999we have explained that recitation
of al-Faatihah is waived for the person praying behind an imam in two
cases:
1 – If he catches up with the imam when he is bowing
2 – If he catches up with the imam just before he bows, and he cannot
complete the recitation of al-Faatihah
SeeAhkaam Hudoor al-Masaajid(p. 141-143) by Shaykh 'Abd-Allaah ibn
Saalih al-Fawzaan.