Hadith: Whoever is prevented from doing something because of his belief in bad omens has thus committed polytheism. They said: What is the expiation of that? He said: It is to say: "O Allah, there is no good except Your good, nor omen except Your omen, and there is no god but You

عن عبد الله بن عمرو بن العاص - رضي الله عنه- مرفوعاً: "مَن ردته الطِّيَرَة عن حاجته فقد أشرك، قالوا: فما كفارة ذلك؟ قال: أن تقول: اللهم لا خير إلا خيرك، ولا طَيْرَ إِلَّا طَيْرُكَ ولا إله غيرك".
[صحيح] - [رواه أحمد]

‘Abdullāh ibn ‘Amr ibn al-‘Ās (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: “Whoever is prevented from doing something because of his belief in bad omens has thus committed polytheism. They said: What is the expiation of that? He said: It is to say: "O Allah, there is no good except Your good, nor omen except Your omen, and there is no god but You.’”
[Authentic hadith] - [Narrated by Ahmad]

Explanation

The Messenger of Allah (may Allah’s peace and blessings be upon him) informs us that whoever refrains from doing anything that he had intended to do out of belief in bad omens, has in some sense committed polytheism. When the Companions asked him about the expiation of this major sin, he instructed them to say those noble words mentioned in the Hadīth. This homily indicates entrusting all affairs to Allah and negating omnipotence from anyone other than Him.