In the name of Allah, the Gracious, the Merciful
Al-Nawawi records in his book Riyad al-Salihin:
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:
إِذَا أَصْبَحَ أَحَدُكُمْ يَوْمًا صَائِمًا فَلَا يَرْفُثْ وَلَا يَجْهَلْ فَإِنْ امْرُؤٌ شَاتَمَهُ أَوْ قَاتَلَهُ فَلْيَقُلْ إِنِّي صَائِمٌ إِنِّي صَائِمٌ
When one of you wakes up in the morning for fasting, then he should not use obscene language or behave foolishly. If anyone abuses him or fights with him, he should say twice: Indeed, I am fasting.
Source: Ṣaḥīḥ Muslim 1151, Grade: Sahih
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:
مَنْ لَمْ يَدَعْ قَوْلَ الزُّورِ وَالْعَمَلَ بِهِ فَلَيْسَ لِلَّهِ حَاجَةٌ فِي أَنْ يَدَعَ طَعَامَهُ وَشَرَابَهُ
Whoever does not leave evil words and deeds while fasting, Allah does not need him to leave food and drink.
Source: Ṣaḥīḥ al-Bukhārī 1903, Grade: Sahih
In another narration, the Prophet said:
رُبَّ صَائِمٍ لَيْسَ لَهُ مِنْ صِيَامِهِ إِلَّا الْجُوعُ
One might fast and he gets nothing from his fast but hunger.
Source: Sunan Ibn Mājah 1690, Grade: Sahih
Abu Huraira reported: The Messenger of Allah, peace and blessings be upon him, said:
مَنْ نَسِيَ وَهُوَ صَائِمٌ فَأَكَلَ أَوْ شَرِبَ فَلْيُتِمَّ صَوْمَهُ فَإِنَّمَا أَطْعَمَهُ اللَّهُ وَسَقَاهُ
Whoever mistakenly eats or drinks while he is fasting, let him complete his fast for Allah has fed him and given him drink.
Source: Ṣaḥīḥ al-Bukhārī 1933, Grade: Muttafaqun Alayhi
Laqit ibn Sabirah reported: The Messenger of Allah, peace and blessings be upon him, said:
أَسْبِغْ الْوُضُوءَ وَخَلِّلْ بَيْنَ الْأَصَابِعِ وَبَالِغْ فِي الِاسْتِنْشَاقِ إِلَّا أَنْ تَكُونَ صَائِمًا
Perform ablution well, clean the base of your fingers, and sniff water deep into your nose, unless you are fasting.
Source: Sunan al-Tirmidhī 788, Grade: Sahih
Aisha, may Allah be pleased with her, said:
أَنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ كَانَ يُدْرِكُهُ الْفَجْرُ وَهُوَ جُنُبٌ مِنْ أَهْلِهِ ثُمَّ يَغْتَسِلُ وَيَصُومُ
The Messenger of Allah, peace and blessings be upon him, would wake up at dawn in a state of major impurity, then he would perform a ritual bath and observe fasting.
Source: Ṣaḥīḥ al-Bukhārī 1925, Grade: Muttafaqun Alayhi
Success comes from Allah, and Allah knows best.