On Fridays, after the azan is called for the Friday prayer, our imam sits on the pulpit and gives a lecture in Bangla. After the lecture, he tells us to pray four units of sunnah prayer. After the sunnah prayer, azan is made inside the mosque, and then the imam stands up on the pulpit and gives the sermon in Arabic, after that, he leads us in the two-unit congregational prayer. I know that the lecture he gives in Bangla and the four-unit sunnah prayer are innovations, and the sermon that he gives in Arabic is also an innovation because most of us do not understand Arabic. Allaah says in the Quran (interpretation of the meaning): {O you who have believed, when [the azan] is called for the prayer on the day of Jumu’ah [Friday], then proceed to the remembrance of Allaah and leave trade. That is better for you, if you only knew.} And there is also a hadith from which we know that angels keeps record of those who enter the mosque until the imam sits on the pulpit to give the sermon. My question is: is it permissible for me to go to the mosque late, just before the sermon in Arabic starts? The reason is that I do not want to support innovations. Will I be sinful for going to the mosque late? Will I get less reward?Please note that most of the imams in my country follow this innovation and that there is not a single Ahlus Sunnah mosque near to my home; they are really far away, and it is difficult for me to go to an Ahlus Sunnah mosque.

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, sallallaahu ʻalayhi wa sallam, is His slave and Messenger. 

Delivering the Friday sermon in other than Arabic for people who do not understand Arabic is not a bid'ah (religious innovation). It is better for the imaam to deliver the khutbah in Arabic and then translate it or deliver it in another language only.

The Fatwa of the Permanent Committee for Islamic Research and Fatwas reads:

“In countries whose population or most of them do not know Arabic, the imaam may give the sermon in Arabic and then translate it into their language so that they understand his preaching and benefit of it. He may also give the sermon in their language only though it is not Arabic. However, giving the sermon in Arabic and then translating it to the audience is better so as to follow the guidance of the Prophet, sallallaahu ʻalayhi wa sallam, in this regard and realize the ultimate purpose and objective of the sermon while avoiding the area in which there is a scholarly difference of opinion.” For more benefit, please refer to fatwa 81486.

There is no harm in giving a lecture in Bangla, as has previously been underlined in fatwa 85175 highlighting that there is no objection to give a sermon before the Friday sermon if this is beneficial for the people as long as this is not done regularly and not considered as an act of Sunnah that should be done on Fridays since neither the Messenger of Allaah, sallallaahu ʻalayhi wa sallam, nor the companions or their rightly guided predecessors have done that.

As for the imaam's instructions for the worshipers to perform four rakʻahs (units of prayer) before the sermon, if he intends these rakʻahs to be a Sunnah prayer before the Friday prayer, then the scholarly view adopted at Islamweb is that there is no reported Sunnah prayer prescribed before the Friday prayer. Some marfoo’ ahaadeeth (i.e. ahaadeeth that are directly attributed to the Prophet, sallallaahu ‘alayhi wa sallam) have been reported in this regard, but they are not authentic like the hadeeth narrated on the authority of Ibn ʻAbbaas in which it was said that the Prophet, sallallaahu ʻalayhi wa sallam, used to perform four rakʻahs before the Friday prayer...” [Ibn Maajah] Scholars of hadeeth declared its chain of narration weak. However, it has been reported on the authority of ʻAtaa’ ibn As-Saa'ib that Abu ʻAbd Ar-Rahmaan As-Sulami said, “ʻAbdullaah (ibn Masʻood) used to command us to perform four rakʻahs before the Friday prayer and four after it.” [Musannaf ʻAbd Ar-Razzaaq]

Al-Albaani stated that the chain of narration of this hadeeth is sound and void of defects.

As for your question whether it is permissible for the Muslim to go to the mosque late, you should know that the Muslim is enjoined to go the mosque to attend the Friday prayer right after the athaan is raised. Allaah, The Exalted, says (what means): {O you who have believed, when (the azan) is called for the prayer on the day of Jumuʻah (Friday), then proceed to the remembrance of Allaah...} [Quran 62:9] Ibn Katheer wrote, “The athaan mentioned in the verse is the second athaan, which was raised when the Prophet, sallallaahu ʻalayhi wa sallam, came out of his house and sat on the pulpit...” So, when the athaan is raised as the imaam ascends the pulpit to deliver the sermon, it is obligatory on you to hasten to the mosque.

As for the question whether arriving late would make you lose some of the reward, there is no doubt that the delay decreases the reward; he who goes to the mosque early to attend the Friday prayer earns a greater reward than he who goes late. The Prophet, sallallaahu ʻalayhi wa sallam, said:

“He who performs ghusl (ritual bath) on Friday and then goes (to the mosque) is like one who offers a she-camel as a sacrifice, and he who comes at the second hour is like one who offers a cow, and he who comes at the third hour is like one who offers a horned ram, and he who comes at the fourth hour is like one who offers a hen, and he who comes at the fifth hour is like one who offers an egg. And when the imaam comes out, the angels come and listen to the mention of Allaah (the sermon).” [Al-Bukhari and Muslim]

So you should be keen on going to the mosque for the Friday prayer early so as to earn greater rewards.

Allaah knows best.