Imam al-Dhahabi mentions in great biographical encyclopedia of the salaf, Siyaar ‘Alaam al-Nubala‘, when discussing Imam Maalik ibn Anas:
إن عبد الله العمري العابد كتب إلى مالك يحضه على الانفراد والعمل فكتب إليه مالك: إن الله قسم الأعمال كما قسم الأرزاق فرب رجل فتح له في الصلاة ولم يفتح له في الصوم وآخر فتح له في الصدقة ولم يفتح له في الصوم وآخر فتح له في الجهاد.
فنشر العلم من أفضل أعمال البر وقد رضيت بما فتح لي فيه وما أظن ما أنا فيه بدون ما أنت فيه وأرجو أن يكون كلانا على خير وبر.
Abdullah al-‘Umari the ‘aabid (devoted worshiper) once wrote to Maalik urging him to focus his efforts solely on performing acts of worship [i.e. that he ought to cut back on his efforts in teaching and spreading knowledge in order to focus more on ‘ibaadah]. So Maalik wrote back to him:
“Indeed Allah has distributed people’s actions (talents) just as He has distributed their sustenance. So perhaps He made salaat easy for someone whereas He did not make fasting easy for him. And for another He made giving sadaqah easy for them, and did not make fasting easy for them. And for another he made jihaad easy for them.
Thus spreading knowledge is one of the most virtuous righteous actions, and I am pleased with what Allah has made easy for me. And I do not think that what I am doing is of lesser value than what you are doing, and I hope that both of us are upon good and righteousness.”
[Siyaar ‘Alaam al-Nubala‘ 8/114]
See also: Ibn al-Qayyim on Patience