פירוש על שמואל א 12:23

And as for me, far be it from me. Since you will do your part by returning to 'ה, I also, far be it from me to stop praying on your behalf.¹⁴ From this verse, the Gemara in Maseches Berachos 12b, derives, that if a person knows that his prayers will be answered if he prays for mercy for his fellow but refrains from doing so, he is considered to have sinned.