Assalamualaikum ustaz. Was my Friday prayer considered accepted if I was late and only get to follow the imam in the second rakaat? Should I just add one rakaat or perform the Zohor prayer? Hope for an explanation.
Waalaikumussalam wrt. wbt.,
Alhamdulillah, praise and gratitude to Allah SWT for His countless blessings for us all. Praise and salutations to our beloved Prophet Muhammad PBUH, his family, companions, and all those who follow his footsteps until the Final day.
We begin with Allah SWT’s statement:
يَا أَيُّهَا الَّذِينَ آمَنُوا إِذَا نُودِيَ لِلصَّلَاةِ مِن يَوْمِ الْجُمُعَةِ فَاسْعَوْا إِلَىٰ ذِكْرِ اللَّـهِ وَذَرُوا الْبَيْعَ ۚ ذَٰلِكُمْ خَيْرٌ لَّكُمْ إِن كُنتُمْ تَعْلَمُونَ
“O you who have believed, when [the adhan] is called for the prayer on the day of Jumu’ah [Friday], then proceed to the remembrance of Allah and leave trade. That is better for you, if you only knew.” 
According to Syeikh al-Sa’di, this verse taught us that Allah SWT commanded His believing slaves to hasten to the mosque to perform the Friday prayer as soon as the adhan is called out and making the Friday prayer our number one priority. 
The meaning of ‘فَاسْعَوْا إِلَىٰ ذِكْرِ اللَّـهِ’ (then proceed to the remembrance of Allah) according to scholars, they interpreted it as hastening to listen to the Friday sermon and perform the Friday prayer after it. 
While Imam Syaukani said: Allah SWT commanded in His honoured book to hasten in remembering Him. And the sermon is a form of dhikrullah. Even if the sermon is not included in the meaning of dhikrullah, its ruling is fardhu. 
Islam prohibits any form of distracting activity when the muezzin has called the second adhan based on the above statement of Allah SWT. Syeikh Jalaluddin al-Mahalli stated: “The commanding word on the verse shows its obligation in this context it is stated through the mentioning of leaving trade and it is prohibited to be engaged in it after the second adhan. It is analogically deduced with trade is all the activities we’ve explained, for its meaning is the same as trade in the issue of distracting from Friday prayer.” 
Whereas Syeikh ‘Umairah explained: The guidance in this verse for a person whose house is very near to the jami’ mosque and he’s certain that he’ll still get the Friday if he came midway through the sermon, (it is still) prohibited for him to stay at his house because his engagement at home with his family or other matters, moreover, it is obligatory for him to hasten to the jami’ mosque heeding the statement of Allah SWT, ‘إِذَا نُودِيَ لِلصَّلَاةِ…’ (when [the adhan] is called for the prayer…)” 
Furthermore, there are numerous other hadiths that instruct a person to attend the mosque early for the purpose of performing the Friday prayer. Among them is a hadith narrated by Abu Hurairah RA, the Prophet PBUH said:
مَنِ اغْتَسَلَ يَوْمَ الجُمُعَةِ غُسْلَ الجَنَابَةِ ثُمَّ رَاحَ، فَكَأَنَّمَا قَرَّبَ بَدَنَةً، وَمَنْ رَاحَ فِي السَّاعَةِ الثَّانِيَةِ، فَكَأَنَّمَا قَرَّبَ بَقَرَةً، وَمَنْ رَاحَ فِي السَّاعَةِ الثَّالِثَةِ، فَكَأَنَّمَا قَرَّبَ كَبْشًا أَقْرَنَ، وَمَنْ رَاحَ فِي السَّاعَةِ الرَّابِعَةِ، فَكَأَنَّمَا قَرَّبَ دَجَاجَةً، وَمَنْ رَاحَ فِي السَّاعَةِ الخَامِسَةِ، فَكَأَنَّمَا قَرَّبَ بَيْضَةً، فَإِذَا خَرَجَ الإِمَامُ حَضَرَتِ المَلاَئِكَةُ يَسْتَمِعُونَ الذِّكْرَ
“If someone does ghusl for major ritual impurity on the day of jumuah and then goes in the first part of the time, it is as if he had offered up a camel. If he goes in the second part of the time, it is as if he had offered up a cow. If he goes in the third part of the time, it is as if he had offered up a horned ram. If he goes in the fourth part of the time, it is as if he had offered up a hen. If he goes in the fifth part of the time, it is as if he had offered up an egg. And when the imam comes out, the angels settle down listening to the dhikr (remembrance of Allah).” 
Among the matters that can be understood from the above hadith is that the Muslims are instructed to attend the mosque early due to the great rewards stated in the hadith. It is also stated by Imam al-Nawawi RA: “Our ashab and others have agreed that it is sunnah to attend the Friday prayer early in the first part of it according to the previous hadith (the above hadith). Considering the times mentioned above, there are three opinions:
- At dawn and this is chosen by the author (Imam al-Syirazi) and most scholars.
- After the sun has risen and this is not the chosen opinion in the book al-Tanbih and it contradicts this opinion for those who hold unto it.
- The times meant is the short interval after the sun passes its zenith and this is chosen by al-Qadhi Husain, Imam al-Haramain and other than them from Khurasan and madhhab Malik. 
According to the book al-Mu’tamad in madhhab al-Syafie, the above-mentioned times starts at dawn because it is the beginning of the sanctioning (of Friday prayer) and it is also permissible to perform the sunnah Friday bath.
At the end of the hadith, it is stated that the angels hear the sermon when the imam exits. This shows that whoever attends it after the imam exits will not receive the rewards of those who attend the Friday prayer early. Furthermore, the sanctioning of arriving early at the mosque is an encouragement for people to attain the advantages stated in the hadith و to receive the advantages of the first saf, waiting and busying oneself with sunnah deeds and dhikr or others. All of these will never be attained by a person who goes to the mosque after the sun has passes its zenith and he’ll also not receive the advantages if he arrives after the sun has passes its zenith for that is the time the adhan is called. 
The Issue of Only Having the Time to Perform One Rakaat of Friday Prayer
Regarding the above question, if he gets to perform one rakaat together with the imam, then he attained his Friday. This is based on a hadith of the Prophet PBUH:
مَنْ أَدْرَكَ رَكْعَةً مِنَ الصَّلاَةِ، فَقَدْ أَدْرَكَ الصَّلاَةَ
“If anyone obtains a rak’ah in the prayer (along with the imam), he has obtained the whole prayer.” 
Since he managed to follow one rakaat with the imam, then he only has to add another rakaat of his prayer. Form Abu Hurairah RA, Rasullullah PBUH said:
مَنْ أَدْرَكَ مِنَ الْجُمُعَةِ رَكْعَةً فَلْيُصَلِّ إِلَيْهَا أُخْرَى
“Whoever catches one Rak’ah of Friday, let him add another Rak’ah to it.” 
However, if he didn’t get even one rakaat with the imam, he has to add another four rakaat for Zuhur prayer. For example, if he arrives when the imam is performing the final tahiyyat. The reason is the Friday prayer must be performed in a congregation. From Tariq bin Syihab RA, the Prophet PBUH said:
الْجُمُعَةُ حَقٌّ وَاجِبٌ عَلَى كُلِّ مُسْلِمٍ فِي جَمَاعَةٍ
“The Friday prayer in congregation is an obligatory duty upon every Muslim,” 
The author of al-Fiqh al-Mnahaji stated: Indeed, the congregational prayer in Friday prayer must be at least one complete rakaat. Hence, if he gets only one rakaat then his Friday is valid. 
In Syarh al-Zad and its Hasyiah, it is stated: “Whoever gets to follow the imam one rakaat in Friday prayer, then he should complete another rakaat through the ijamk. However, if he didn’t manage to even get one rakaat – such as the imam is standing for I’tidal on the second rakaat, then a person arrives and quickly follows the imam – then he should complete the four rakaat Zuhur prayer.”