Sahih al-Bukhari — Military Expeditions led by the Prophet (pbuh) (Al-Maghaazi) — Hadith No: 4118

Narrated Ka`b bin Malik:I never failed to join Allah's Messenger (ﷺ) in any of his Ghazawat except in the Ghazwa of Tabuk. However, I did not take part in the Ghazwa of Badr, but none who failed to take part in it, was blamed, for Allah's Messenger (ﷺ) had gone out to meet the caravans of (Quraish, but Allah caused them (i.e. Muslims) to meet their enemy unexpectedly (with no previous intention)

Narrated Ibn `Abbas:On the day of the battle of Badr, the Prophet (ﷺ) said, "O Allah! I appeal to You (to fulfill) Your Covenant and Promise. O Allah! If Your Will is that none should worship You (then give victory to the pagans)." Then Abu Bakr took hold of him by the hand and said, "This is sufficient for you." The Prophet came out saying, "Their multitude will be put to flight and they will show their backs

Narrated Ibn `Abbas:The believers who failed to join the Ghazwa of Badr and those who took part in it are not equal (in reward)

Narrated Al-Bara:I and Ibn `Umar were considered too young to take part in the battle of Badr