Intention of getting up to perform Tahajjud

"The one who goes to bed with the intention of getting up during the night to perform Salah but sleeps till the morning, will acquire the intention which he had made. As for his sleep, this is a gift from his Rabb." (Mishkaat)

[English version of "L'intention pou levé pou tahajjud" – Al Jamiat – Vol.5 No.9]