Hazrat Moulana Muhammad Ilyaas (rahmatullahi ‘alaih) once mentioned:
In our effort of Da’wat and Tableegh, it is extremely important for one to ensure that his intention remains purely for the sake of Allah Ta‘ala at all times. Our brothers who strive in this work should regard fulfilling the command of Allah Ta‘ala and acquiring His pleasure as their sole purpose and object for doing the work. In proportion to the purity of one’s intention, and the stronger the sincerity one has when carrying out good deeds, one will receive reward by Allah Ta‘ala.
It is a known fact that after striving for Deen, when one begins to see the worldly benefits of one’s sacrifice and striving materialize, then since the fruits and outcome of one’s actions are being witnessed before one’s eyes, one’s reward will decrease. The reason is that (initially, one was only doing the action for the pleasure of Allah Ta‘ala without seeing any worldly benefit, but now since the worldly benefit of the sacrifice is also being witnessed,) the sacrifice is also taking place with acquiring these worldly benefits.
Look at the example of the conquest of Makkah Mukarramah. Before the conquest of Makkah Mukarramah, those who sacrificed their lives and wealth received a greater reward compared to those who sacrificed their lives and wealth after the conquest of Makkah Mukarramah. The reason is that after the conquest of Makkah Mukarramah, the victory of Islam had already been achieved and the Muslims gaining dominance and rulership in the land had been witnessed by the people. (Hence, the level of ikhlaas and sacrifice of those who embraced Islam after the conquest of Makkah Mukarramah was not as great as the level of ikhlaas and sacrifice of those who embraced Islam before the conquest of Makkah Mukarramah).
Therefore, Allah Ta‘ala mentions in the Quraan Majeed:
لَا یَسۡتَوِیۡ مِنۡکُمۡ مَّنۡ اَنۡفَقَ مِنۡ قَبۡلِ الۡفَتۡحِ وَقٰتَلَ ؕ اُولٰٓئِکَ اَعۡظَمُ دَرَجَةً مِّنَ الَّذِیۡنَ اَنۡفَقُوۡا مِنۡۢ بَعۡدُ وَقٰتَلُوۡا ؕ وَکُلًّا وَّعَدَ اللّٰه الۡحُسۡنٰی ؕ
Those from among you (i.e. the Sahaabah) who spent wealth before the conquest (of Makkah Mukarramah) and fought (in the path of Allah Ta‘ala) are not equal (to those among you who spent wealth and fought in the path of Allah Ta‘ala after the conquest of Makkah Mukaramah). Those (who spent wealth and fought before the conquest) are greater in rank than those who spent wealth and fought later on, though for both groups, Allah has promised a good reward. (Surah Hadeed v10)
(Malfoozaat Hazrat Moulana Muhammad Ilyaas [rahmatullahi ‘alaih] pg. 68)
Source: Ihyaauddeen.co.za