(At-Thouba) 9 : 92
وَلَا عَلَى الَّذِينَ إِذَا مَا أَتَوْكَ لِتَحْمِلَهُمْ قُلْتَ لَا أَجِدُ مَا أَحْمِلُكُمْ عَلَيْهِ تَوَلَّوْا وَأَعْيُنُهُمْ تَفِيضُ مِنَ الدَّمْعِ حَزَنًا أَلَّا يَجِدُوا مَا يُنْفِقُونَ

And nor is there blame upon those who, when they came to you that you might undertake them, you said: I am not finding any means for bearing you. They returned with their eyes overflowed with tears out of grief that they couldn’t find something to spend.

Due to a lack of vehicles, food, and weapons, some weaklings couldn’t go out with Messenger for Tabuk Expedition. They were among the best servants of Impartial Lord because even though they couldn’t participate bodily, their soul participated with Messenger. On returning from Tabuk to Medina, Messenger told about these sincere believers to his companions as “There are some in Medina who have followed you in each of your footsteps and who have passed each valley that you crossed”. The companions asked: “While they are at Medina itself?!” The Messenger replied: “Yes, while they are at Medina. They would have been with you if they were not forced to withdraw due to the inevitable circumstances”. 

Deeds are rewarded according to one's intentions. Any deed without the participation of the soul will not be accepted as explained in verse 4: 100. See explanations 2: 186, 261 and 3: 127-128.