If I'm late for Zuhr prayer, can I combine it with Asr or must I pray the Zuhr separately from the Asr?
You may say Zuhr and Asr prayer togather and also Maghrib and Esha togather to avoid unnecessary hardship
Ibn 'Abbas reported:
"The Messenger of Allah (peace be upon him) observed the noon and afternoon prayers together, and the sunset and Isha' prayers together without being in a state of fear or in a state of journey." -Saheeh Muslim
The Prophet Muhammad (peace be upon him) said:
"Whoever joins two Prayers together without a legal excuse, he then commits a major sin."
You can't say two Salaat together if you don't have a proper reason. It is best to say your prayers in time.
Imaam Ahmad said that the one who does not pray because of laziness is a kaafir. (Al-Sharh al-Mumti’ ‘ala Zaad al-Mustanqi’, 2/26).Source
Anas ibn Maalik said:
“The Messenger of Allah(saw) said: ‘If one of you sleeps and misses a prayer, or forgets it, then let him pray it as soon as he remembers, because Allah(swt) says (interpretation of the meaning): ‘… and perform al-salaah for My remembrance.’ [Ta-Ha 20:14]” (Reported by Muslim). Source
Delaying the prayer intentionaly: Many workers delay Zuhr and Asr Prayer till night-time. Quran speaks strictly on guarding our Salat:
“Guard strictly (five obligatory) As-Salawat (the prayers) especially the middle Salat >(i.e. Asr Prayers)”
[The Holy Quran, 2:238]
There are Fiqh-us-Sunnah about combining two prayers under certain circumstances:
- Combining the salah at 'Arafa and al-Muzdalifah
- Combining the salah during traveling
- Combining two prayers during rain
- Combining the two prayers due to some illness or other excuse
- Combining two prayers due to some pressing need
And many more.... detailed informations: Fiqh-us-Sunnah, Volume 2: Combining two prayers
You may (it is permissible to) pray Dhur and Asr together even if you are not on travel. You can also pray Maghrib and Isha' together if you wish even if you are not traveling.
The Prophet used to make Dhur and asr together, and Maghrib and Isha' Together in Madinah when there was no danger, rain, or travel.
And that is by making Dhuhr and Asr together, making it eight Rak'at, and making Maghrib and Isha' together making it seven Rak'ats, source.
The Prophet (peace and blessings be upon Him) did this so that there will be no unnecessary hardship.
For further reading see this (it is in Arabic).
if you mean that you are out of the time of zuhr, then you cannot combine them, you should make kaza of zuhr.
if you meant that you are just close to end of zuhr time but inside of it, then, i tend to think that you can pray zuhr, than wait for beginning of asr, and pray asr, and it is named combining of prayers , as far as i know.
I was taught that the prophet (saw) would pray Thur at its latis, or before the shadows become double lighth,and then would get up and pray the asr right behind it,so right before Thur go's out and asr is coming in,so there would be a pause in-between, this is the understand I got,how can you pray asr salat if its not in,and ALLAH knows best!