Is it permissible to respond with "Paradise welcomes you" to someone who says "Marḥaban" (welcome), and is this phrase correct?

"مرحبًا" should be responded to with something similar or better, such as "مرحبًا وأهلاً (Marhaban wa Ahlan - Welcome and hello/welcome and you are among family)," in accordance with Allah Almighty's saying: ﴿وَإِذَا حُيِّيتُمْ بِتَحِيَّةٍ فَحَيُّوا بِأَحْسَنَ مِنْهَا أَوْ رُدُّوهَا إِنَّ اللَّهَ كَانَ عَلَى كُلِّ شَيْءٍ حَسِيبًا ﴾ (And when you are greeted with a greeting, greet [in return] with one better than it or return it [in a like manner]. Indeed, Allah is ever, over all things, an Accountant.)

As for the saying "ترحب بك الجنة (May Paradise welcome you)," if it is intended as a statement of fact, it is a lie and impermissible. If it is intended as a supplication, we do not know that Paradise itself welcomes those who enter it. Rather, the angels welcome the people of Paradise, as stated in the verses: ﴿وَسِيقَ الَّذِينَ اتَّقَوْا رَبَّهُمْ إِلَى الْجَنَّةِ زُمَرًا حَتَّى إِذَا جَاءُوهَا وَفُتِحَتْ أَبْوَابُهَا وَقَالَ لَهُمْ خَزَنَتُهَا سَلَامٌ عَلَيْكُمْ طِبْتُمْ فَادْخُلُوهَا خَالِدِينَ﴾ (And those who feared their Lord will be driven to Paradise in groups until, when they reach it while its gates have been opened and its keepers will say to them, "Peace be upon you; you have become pure; so enter it to abide eternally therein.") and ﴿جَنَّاتُ عَدْنٍ يَدْخُلُونَهَا وَمَنْ صَلَحَ مِنْ آبَائِهِمْ وَأَزْوَاجِهِمْ وَذُرِّيَّاتِهِمْ وَالْمَلَائِكَةُ يَدْخُلُونَ عَلَيْهِمْ مِنْ كُلِّ بَابٍ (23) سَلَامٌ عَلَيْكُمْ بِمَا صَبَرْتُمْ فَنِعْمَ عُقْبَى الدَّارِ﴾ (Gardens of perpetual residence, which they will enter, as well as those who acted righteously among their fathers, their spouses, and their offspring. And the angels will enter upon them from every gate, [saying], "Peace be upon you for what you patiently endured. And excellent is the final home.") and ﴿لَا يَحْزُنُهُمُ الْفَزَعُ الْأَكْبَرُ وَتَتَلَقَّاهُمُ الْمَلَائِكَةُ هَذَا يَوْمُكُمُ الَّذِي كُنْتُمْ تُوعَدُونَ﴾ (The greatest terror will not grieve them, and the angels will meet them, [saying], "This is your Day which you were promised.")

Matters of the unseen are by divine decree, and one should not speak about them except with evidence. Since it has not been established that Paradise welcomes its inhabitants, it is better to avoid saying this, lest it be considered an excess in supplication. Abdullah ibn Mughaffal heard his son say, "O Allah, I ask You for the white palace to the right of Paradise when I enter it." He said, "My son, ask Allah for Paradise and seek refuge with Him from the Fire, for I heard the Messenger of Allah, peace and blessings be upon him, say: «There will be people in this Ummah who will exceed the bounds in purification and supplication»." Therefore, this phrase should be avoided, and the customary greetings and welcomes should be used.