Assalamualaikum ustaz. I’ve performed the jamak for Zohor and Asar during my travel. However, when I arrive at my destination, I find that the time for Asar hasn’t begun. What is the status of my prayer?
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 Last Day.
Allah SWT gives a facilitation (rukhsah) for travellers to perform their prayers through jamak and qasar. Allah SWT states in the Quran:
وَإِذَا ضَرَبْتُمْ فِي الْأَرْضِ فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَقْصُرُوا مِنَ الصَّلَاةِ إِنْ خِفْتُمْ أَن يَفْتِنَكُمُ الَّذِينَ كَفَرُوا ۚ إِنَّ الْكَافِرِينَ كَانُوا لَكُمْ عَدُوًّا مُّبِينًا
“And when you travel throughout the land, there is no blame upon you for shortening the prayer, [especially] if you fear that those who disbelieve may disrupt [or attack] you. Indeed, the disbelievers are ever to you a clear enemy.” 
Among the valid condition of jamak takdim or ta’khir is a person must be travelling. The author of the book al-Fiqh al-Manhaji stated that among the valid conditions of jamak taqdim is as follows: “One must still be travelling when he is starting to perform the second prayer. Then it is not an issue if he arrives at his place of origin when the second prayer time hasn’t ended.”
While among the valid conditions of jamak ta’khir is: “One must still be travelling until he finishes both prayers. Thus, if he arrives before both the prayers are completed, then the later prayer becomes a qadha’ prayer.” 
In the above issue, jamak and qasar prayers that you performed is valid. It is unnecessary to repeat said prayers. Form Abdullah bin Umar R.Anhuma, he heard the Messenger PBUH say:
لَا تُصَلُّوا صَلَاةً فِي يَوْمٍ مَرَّتَيْنِ
“Do not pray a prayer twice on the same day.” 
Though, if a person arrives at the mosque and finds that people are performing the obligatory prayer in congregation, for instance, the Asar prayer, then it is prioritized for him to repeat the prayer together with them as a sunnah prayer. In a hadith from Yazid bin Aswad RA, where he said:
صَلَّى رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ الْفَجْرَ بِمِنًى فَانْحَرَفَ فَرَأَى رَجُلَيْنِ وَرَاءَ النَّاسِ فَدَعَا بِهِمَا فَجِيءَ بِهِمَا تَرْعَدُ فَرَائِصُهُمَا فَقَالَ مَا مَنَعَكُمَا أَنْ تُصَلِّيَا مَعَ النَّاسِ فَقَالَا قَدْ كُنَّا صَلَّيْنَا فِي الرِّحَالِ قَالَ فَلَا تَفْعَلَا إِذَا صَلَّى أَحَدُكُمْ فِي رَحْلِهِ ثُمَّ أَدْرَكَ الصَّلَاةَ مَعَ الْإِمَامِ فَلْيُصَلِّهَا مَعَهُ فَإِنَّهَا لَهُ نَافِلَةٌ
“The Messenger PBUH performed the subuh prayer in Mina. When he (the Prophet) had prayed there were two persons (sitting) in the corner of the mosque; they did not pray (along with the Prophet). He called for them. They were brought trembling (before him). He asked: What prevented you from praying along with us? They replied: We have already prayed in our houses. He said: Do not do so. If any of you prays in his house and finds that the imam has not prayed, he should pray along with him; and that will be a supererogatory prayer for him.” 
We state this is the prioritized.