Sahih Muslim Book 33, Hadith Number 6403.

Chapter : The growth of a child in the womb of a mother and his destiny in regard to his livelihood, his deeds. both good and evil.

This hadith has been transmitted on the authority of Jabir b. Abdullah with the same wording (and includes these words): ” Allah’s Messenger (may peace be upon him) said: Every doer of deed is facilitated in his action.”