Question Summary:
I made a vow of tahajjud, 500 durood daily and Quran completion monthly but I cannot keep up with it?

Question Detail:

I made a vow that if my problem is solved I will pray tahajjud, 500 times durood daily and finish one quran every month.  I did that for sometime but now it is very hard to do.  I pray tahajjud and durood 300 times but I have started memorising the Quran and tafseer, I become so tired at the end of the day.  Please tell me some kaffaarah.

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
 
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
 
A vow becomes binding verbally using words which customarily refer to a vow.  If you merely thought of the following and did not verbally utter the words binding these actions then this vow will be invalid and you will not be bound to anything.[1] 
 
Once a vow is made, it becomes binding on the individual.  Kaffārah will not absolve one from a vow.  One will have to carry out the vowed action.[2]
 
If the a vow was made in the above manner, then tahajjud, durūd shareef have become binding.[3]
There is a difference of opinion with regards to the binding of the recitation of the Qur῾ān.   You should do your utmost to abide by the vow of completing one Qur῾ān a month.  Do not consider it a burden; envisage it as a blessing to gain proximity to Almighty Allah.[4]
 
You should recite the shortest durūd shareef which is:
 
صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ
 
Keep a misbaha (rosary beads) with you and read durūd shareef where ever you go.  To recite the above will take 10-15 minutes at the most.  So during the day you can read anytime and anywhere to reach 500.  You neither need wudhū to recite durūd shareef.
 
As for tahajjud, one opinion regarding tahajjud is that it refers to any salāh after the fardh of ῾isha.[5]  Hence, perform two rak῾<span