Hadith: Verily, the reward of deeds depends on intentions, and each person will be rewarded according to what he intended

عَنْ أَمِيرِ المُؤْمِنِينَ أَبِي حَفْصٍ عُمَرَ بْنِ الخَطَّابِ رضي الله عنه قَالَ: سَمِعْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَقُولُ:
«إنَّمَا الأَعْمَالُ بِالنِّيَّاتِ، وَإِنَّمَا لِكُلِّ امْرِئٍ مَا نَوَى، فَمَنْ كَانَتْ هِجْرَتُهُ إلَى اللَّهِ وَرَسُولِهِ فَهِجْرَتُهُ إلَى اللَّهِ وَرَسُولِهِ، وَمَنْ كَانَتْ هِجْرَتُهُ لِدُنْيَا يُصِيبُهَا أَوْ امْرَأَةٍ يَنْكِحُهَا فَهِجْرَتُهُ إلَى مَا هَاجَرَ إلَيْهِ».
[صحيح] - [رواه إماما المحدثين أبو عبد الله محمد بن إسماعيل بن إبراهيم بن المغيرة بن بردزبه البخاري، وأبو الحسين مسلم بن الحجاج بن مسلم القشيري النيسابوري في صحيحيهما اللذين هما أصح الكتب المصنفة] - [الأربعون النووية: 1]

The Commander of the Believers, Abu Hafs ‘Umar ibn al-Khattāb (may Allah be pleased with him) reported: I heard the Messenger of Allah (ﷺ) say:
"Verily, the reward of deeds depends on intentions, and each person will be rewarded according to what he intended. So, he whose emigration is for the sake of Allah and His Messenger, his emigration will be for the sake of Allah and His Messenger, and he whose emigration is to achieve some worldly gain or take some woman in marriage, his migration will be for what he has migrated for."
[Authentic hadith] - [رواه إماما المحدثين أبو عبد الله محمد بن إسماعيل بن إبراهيم بن المغيرة بن بردزبه البخاري وأبو الحسين مسلم بن الحجاج بن مسلم القشيري النيسابوري في صحيحيهما اللذين هما أصح الكتب المصنفة] - [الأربعون النووية - 1]

Explanation

The Prophet (may Allah's peace and blessings be upon him) explains that all deeds are considered according to the intention behind them. This ruling generally applies to all deeds, including acts of worship and dealings. So, he who seeks by his deed some worldly benefit will attain that benefit and will not be rewarded for it. And he who performs a deed with the intention to draw close to Allah Almighty will be rewarded, even if his deed is an ordinary one, like eating and drinking.
Then, the Prophet (may Allah's peace and blessings be upon him) provided an example to illustrate the impact of intention while both deeds apparently look equal. He pointed out that if a person migrates and leaves his homeland with the intention to win the pleasure of his Lord, his migration is a Shar‘i and accepted one, for which he will be rewarded, given his sincere intention; and if a person migrates to attain some worldly benefit, like wealth, high standing, business, or a wife, he will not attain anything from his migration except what benefit he intended, and no reward will be given to him.

Benefits from the Hadith

1. The Hadīth urges us to be sincere, for Allah only accepts the deeds that are intended for His sake.
2. If a legally accountable person performs the deeds that are to be done to gain Allah's pleasure by way of habit, he will only be rewarded for them if he intends to draw close to Allah Almighty by doing them.
3. The intention serves to distinguish between acts of worship themselves and also separates acts of worship from habits.