Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) was asked about 'azl, and he said: It is not within the power of the son of Adam to kill a soul that Allah wills to create. She is your tillage; you may keep it thirsty or water it, as you wish.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب النكاح / 14320