aṣ-Ṣabr (الصبر) is one of the more frequently used phrases amongst the Muslims, usually in use when dealing with forbearance upon calamaties or that which may agonize an individual, & persisting upon Allāh’s obedience even with the struggles that come along with doing so.
Allāh says in al-Qurʾān regarding aṣ-Ṣabr:
وَٱسۡتَعِينُواْ بِٱلصَّبۡرِ وَٱلصَّلَوٰةِۚ وَإِنَّهَا لَكَبِيرَةٌ إِلَّا عَلَى ٱلۡخَٰشِعِينَ
And seek help through patience and prayer, and indeed, it is difficult except for the humbly submissive [to Allāh].
– Sūrah al-Baqarah, ʾĀyah 45
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُواْ ٱسۡتَعِينُواْ بِٱلصَّبۡرِ وَٱلصَّلَوٰةِۚ إِنَّ ٱللَّهَ مَعَ ٱلصَّٰبِرِينَ
O you who have believed, seek help through patience and prayer. Indeed, Allāh is with the patient.
– Sūrah al-Baqarah, ʾĀyah 153
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُواْ ٱصۡبِرُواْ وَصَابِرُواْ وَرَابِطُواْ وَٱتَّقُواْ ٱللَّهَ لَعَلَّكُمۡ تُفۡلِحُونَ
O you who have believed, persevere and endure and remain stationed and fear Allāh that you may be successful.
– Sūrah al-ʿImrān, ʾĀyah 200
aṣ-Ṣabr is commonly translated as meaning “patience”, though this meaning is more of a summary of what it actually entails. Scholars have explained & gave definitions on this word, & even wrote entire books specifically pertaining to this word alone, such as ʿUddah aṣ-Ṣābirīn by ibn Qayyim al-Jawzīyyah رحمه الله (d. 751 AH/1350 CE) & Qāʾidah fī aṣ-Ṣabr by Shaykh al-Islām ibn Taymīyyah رحمه الله (d. 728 AH/1328 CE) for examples. In terms of the Scholars’ definitions of aṣ-Ṣabr, they are to proceed, ʾIn shāʾ Allāh.
Shaykh Muḥammad ibn Ṣāliḥ al-‘Uthaymīn رحمه الله (d. 1422 AH/2001 CE) said: “aṣ-Ṣabr is restraining the soul upon obedience to Allāh, restraining it from disobeying Allāh, and restraining it from being angry with what Allāh has decreed.” 
Shaykh Ṣāliḥ al-Fawzān حفظه الله said: “aṣ-Ṣabr linguistically means ‘holding back and barring’, yaʾnī restraining the self from annoyance, containing the tongue from complaints and anger, holding back the limbs from wailing, slapping the face, and tearing the clothes.” 
Shaykh ʿAbd ar-Raḥmān ibn Nāṣir as-Saʾdī رحمه الله (d. 1376 AH/1957 CE) said: “aṣ-Ṣabr pertains to safeguarding one’s self and restraining it by doing what the self dislikes. Ṣabr has three parts:
- Persevere on Allāh’s obedience until one performs it
- Keep away from Allāh’s disobedience until one avoids it
- (Be patient) with the painful parts of the destiny appointed by Allāh to avoid feeling bitterness towards it.” 
May Allāh aid us in all of our affairs & keep us firm upon Islām.
All praise is due to Allāh, may His peace & blessings be upon our final Prophet Muḥammad, his family, his companions, & all those who follow him in guidance.
 Sharḥ Thalāthah al-Uṣūl (شرح ثلاثة الأصول) by Shaykh Muḥammad ibn Ṣāliḥ al-‘Uthaymīn | Page 30
 Sharḥ al-ʿAqīdah al-Wasiṭīyyah (شرح العقيدة الواسطية) by Shaykh Ṣāliḥ al-Fawzān | Page 68
 Tafsīr as-Saʾdī (تفسير السعدي) by Shaykh ʿAbd ar-Raḥmān ibn Nāṣir as-Saʾdī | Sūrah al-Baqarah, ʾĀyah 153
Ṣafīullāh Labīb ibn Salīm ʿAbd al-Malik
6th of Ṣafar 1444