The Apostle of Allah ﷺ said: When a man has sexual intercourse, bathing becomes obligatory (both for the male and the female). In the hadith of Matar the words are: Even if there is no orgasm. Zuhair has narrated it with a minor alteration of words.  

أَنَّ نَبِيَّ اللَّهِ ﷺ قَالَ إِذَا جَلَسَ بَيْنَ شُعَبِهَا الأَرْبَعِ ثُمَّ جَهَدَهَا فَقَدْ وَجَبَ عَلَيْهِ الْغُسْلُ وَفِي حَدِيثِ مَطَرٍ وَإِنْ لَمْ يُنْزِلْ قَالَ زُهَيْرٌ مِنْ بَيْنِهِمْ بَيْنَ أَشْعُبِهَا الأَرْبَعِ  

This hadith is narrated by Qatida with the same chain of transmitters, but with minor alterations. Here instead of the word - (jahada, (ijtahada) has been used, and the words;" Even if there is no orgasm" have been omitted.  

أَنَّ فِي حَدِيثِ شُعْبَةَ ثُمَّ اجْتَهَدَ وَلَمْ يَقُلْ وَإِنْ لَمْ يُنْزِلْ  

There cropped up a difference of opinion between a group of Muhajirs (Emigrants and a group of Ansar (Helpers) (and the point of dispute was) that the Ansar said: The bath (because of sexual intercourse) becomes obligatory only-when the semen spurts out or ejaculates. But the Muhajirs said: When a man has sexual intercourse (with the woman), a bath becomes obligatory (no matter whether or not there is seminal emission or ejaculation). Abu Musa said: Well, I satisfy you on this (issue). He (Abu Musa, the narrator) said: I got up (and went) to 'A'isha and sought her permission and it was granted, and I said to her: 0 Mother, or Mother of the Faithful, I want to ask you about a matter on which I feel shy. She said: Don't feel shy of asking me about a thing which you can ask your mother, who gave you birth, for I am too your mother. Upon this I said: What makes a bath obligatory for a person? She replied: You have come across one well informed! The Messenger of Allah ﷺ said: When anyone sits amidst four parts (of the woman) and the circumcised parts touch each other a bath becomes obligatory.  

اخْتَلَفَ فِي ذَلِكَ رَهْطٌ مِنَ الْمُهَاجِرِينَ وَالأَنْصَارِ فَقَالَ الأَنْصَارِيُّونَ لاَ يَجِبُ الْغُسْلُ إِلاَّ مِنَ الدَّفْقِ أَوْ مِنَ الْمَاءِ وَقَالَ الْمُهَاجِرُونَ بَلْ إِذَا خَالَطَ فَقَدْ وَجَبَ الْغُسْلُ قَالَ قَالَ أَبُو مُوسَى فَأَنَا أَشْفِيكُمْ مِنْ ذَلِكَ فَقُمْتُ فَاسْتَأْذَنْتُ عَلَى عَائِشَةَ فَأُذِنَ لِي فَقُلْتُ لَهَا يَا أُمَّاهْ أَوْ يَا أُمَّ الْمُؤْمِنِينَ إِنِّي أُرِيدُ أَنْ أَسْأَلَكِ عَنْ شَىْءٍ وَإِنِّي أَسْتَحْيِيكِ فَقَالَتْ لاَ تَسْتَحْيِي أَنْ تَسْأَلَنِي عَمَّا كُنْتَ سَائِلاً عَنْهُ أُمَّكَ الَّتِي وَلَدَتْكَ فَإِنَّمَا أَنَا أُمُّكَ قُلْتُ فَمَا يُوجِبُ الْغُسْلَ قَالَتْ عَلَى الْخَبِيرِ سَقَطْتَ قَالَ رَسُولُ اللَّهِ ﷺ إِذَا جَلَسَ بَيْنَ شُعَبِهَا الأَرْبَعِ وَمَسَّ الْخِتَانُ الْخِتَانَ فَقَدْ وَجَبَ الْغُسْلُ  

I and she (the Mother of the Faithful) do it and then take a bath.  

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ قَالَتْ إِنَّ رَجُلاً سَأَلَ رَسُولَ اللَّهِ ﷺ عَنِ الرَّجُلِ يُجَامِعُ أَهْلَهُ ثُمَّ يُكْسِلُ هَلْ عَلَيْهِمَا الْغُسْلُ وَعَائِشَةُ جَالِسَةٌ فَقَالَ رَسُولُ اللَّهِ ﷺ إِنِّي لأَفْعَلُ ذَلِكَ أَنَا وَهَذِهِ ثُمَّ نَغْتَسِلُ