Persecuting, killing, and stealing the wealth from Muslims in Mecca did not satisfy these Quraysh polytheists to leave Muslims alone when they fled to Madina. They continued their devilish plots against the Muslims even after the Muslims immigrated to Medina for safe haven. As we have pointed out before, as soon as the small Muslim community arrived in Medina, the Quraysh wrote letters to the leaders of Medina to drive out Muslims or they will come and kill everyone. You can read further on this here: ‘Quraysh Threatened Madinah’s Leaders For Giving Sanctuary To Muslims’.
Muslims living in Medina were already in a critical situation, where there was no much food for them, since their wealth were stolen by the Quraysh, when they were exiled out of Mecca to Medina.
Their satanic plots never stopped when the Muslims arrived in Medina to find safety. One of Quraysh’s men, raided and tried to steal livestock belonging to the Muslims.
As soon as the Prophet (p) received information on this, he sent some of his companions out in pursuit of the enemy. But they got away.
Read also: ‘Did Quraysh Persecute Muslims When They Fled To Madinah?‘
“The Messenger of God had only spent a few days in Medina, less than ten, after coming back from the expedition to al-Ushayrah, before Kurz b. Jabir al-Fihri raided the herds of Medina. The Messenger of God went out in pursuit of him and reached a valley called Safawan in the region of Badr, but Kurz eluded him and was not caught. This was the first expedition of Badr.” 
“THE RAID IN SAFAWAN, WHICH IS TH FIRST RAID OF BADR
The Apostle stayed only a few nights, less than ten, in Medina when he came back from raiding Al-Ushayra, and then Kurz b. Jabir al-Fihri raided the pasturing camels of medina. The Apostle went out in search of him, until he reached a valley called Safawan, in the neighbourhood of Badr. Kurz escaped him and he could not overtake him. This was the first raid of Badr.” 
Kitab Al-Tabaqat Al-Kabir – Ibn Sa’d:
GHAZWAH IN SEARCH OF KURZ IBN JABIR AL-FIHRI
Then (occurred) the ghazwah in search of Kurz Ibn Jabir al-Fihri in the month of Rabi al-Awwal (September, 623 A.) after the commencement of the thirteenth month from this hijrah. The standard-bearer was Ali Ibn Talib and the flag was white. He left behind Zayd Ibn Harithah as his vicegerent at al-Medina. Kurz Ibn Jabir had raided (Sarh) the pasture land of al-Medina and carried away some animals. …The Apostle of Allah (p) set out in his (Kurz’s) search till he reached a valley known as Safawan in the vicinity of Badr which Kurz Ibn Jabir had crossed. The Apostle of Allah (p) did not find (Yalhaqau) him so he returned to al-Medina.” 
Attack of Kurz bin Jābir and Ghazwah of Safwān – Jamādiyul-Ākhir 2 A.H.
However, despite such vigilance and various Muslim parties constantly making watchful rounds in the surroundings of Medina, the mischief of the Quraish managed to break through. As such, ten days had not passed since the return of the Holy Prophet to Medina when a chieftain of Mecca named Kurz bin JābirFihrī very cunningly along with a company of the Quraish, suddenly raided a pasture of Madīnah, which was situated only three miles from the city and fled with camels, etc., belonging to the Muslims. As soon as the Holy Prophet received news of this, he appointed Zaid bin Ḥārithahra as the Amīr in his absence, and set out in his pursuit along with a group of the Companions. The Holy Prophetsa pursued him until he reached Safwān which is an area close to Badr, but he made good his escape. This Ghazwah is also known as Ghazwah Badratul-Ula.
This raid of Kurz bin Jābir was not a minor Beduin act of plunder, rather, it is definite that he had set out against the Muslims on behalf of the Quraish, with a particular motive. As a matter of fact, is it very likely that he had specifically come with the intention of inflicting injury upon the very person of the Holy Prophet, but upon finding the Muslims vigilant, settled upon the robbery of their camels and ran off. This also demonstrates that the Quraish of Mecca had planned to raid Madīnah so as to utterly destroy the Muslims. It should also be remembered that the Muslims had already been given permission for Jihād by the sword prior to this, and in a sense of self defense they had begun to employ an initial plan of action in this regard as well. However, until now, they had not practically suffered any loss in terms of wealth or lives. However, the raid of Kurz bin Jābir was one which practically inflicted harm upon the Muslims. In other words, even after the acceptance of the challenge of the Quraish, it was the disbelievers who practically initiated battle.” 
Hajjah Aminah Adil:
“THE RAID ON SAFWAN, THE FIRST EXPEDITION TO BADR
The Holy Prophet stayed in Medina only few nights after he returned from the Raid on Ushayra. News was brought to him that Kurz bin Jabir al-Fihri had raided pasturing camels belonging to Medina at a distance of three days journey. The Holy Prophet set out to pursue him at once, and rode till he reached the valley of Safawan, in the neighbourhood of a well named Badr. But Kurz had escaped and he could not catch up with him.” 
Muḥammad Ḥusayn Haykal:
“…when Kurz ibn Jabir al-Fihri, an ally of Quraysh, raided the camels and cattle of Medina. The Prophet immediately led a force after him, appointing Zayd ibn Harithah as his representative during his absence. The force marched until it reached a valley called safawan in the district of Badr and again missed their objective, the said Kurz ibn Jabir al-Fihri. It is to this that biographers refer as the first raid of Badr.” 
Al-Sirah Al-Nabawiyah – Dr.Shawqi Abu Khalil:
“THE CAMPAIGN OF SAFAWAN (THE FIRST CAMPAIGN OF BADR) IN RABI’UL-AWWAL 2 AH.
The Messenger of Allah went out in pursuit of Kurz Ibn Jabir Al-Fihri, who had raided the pasturing camels of Al-Medina. He pursued him until he reached a valley called Safawan, in the vicinity of Badr, but Kurz got away from him and he could not catch him, so he went back to Al-Medina.” 
“…Kurz bin Jabir Al-Fihri rustled some grazing cattle belonging to the Muslims. The Prophet gathered seventy Muhajireen and chased him to Safwan on the outskirts of Badr, but Kurz escaped.” 
Dr. Mustafa As-Sibaa’ie:
“THE FIRST EXPEDITION OF BADR
The Prophet set out with a number of his Companions because a man named Kurz ibn Jaabir Al-Faihree raided grazing livestock that belonged to the inhabitants of Al-Madeenah and stole some camels and other livestock cattle. The Prophet pursued Kurz until he reached the valley of Safwaan, which is situated beside Badr; however, Kurz managed to escape his pursuers, and so the Messenger of Allah and his Companions then returned to Al-Madeenah.” 
The myth that has been purported that the Muslims lived safely in Medina, and were left alone by the Quraysh, is not true as the forgoing early reports have established. The Muslims were constantly being attacked by the Makkans even after they fled to Medina, before the battle of Badr ensued. The Prophet (p), 1400 years ago, had no choice but to start defending his community against the continuous attacks by the Quraysh.
 History of al-Tabari: The: The Foundation of the Community: Muhammad At Al-Madina, volume 7, page 14
 Ibn Ishaq’s Sirat Rasul Allah – The Life of Muhammad – Translated by A. Guillaume, Page 286
 Kitab Al-Tabaqat Al-Kabir, By Ibn Sa’d, volume 2, page 6
 The Life & Character of the Seal of Prophets volume 2 (Sirat Khatamun-Nabiyyin) By Ḥaḍrat Mirza Bashir Aḥmad M.A., page 101 – 102
 Muhammad, the Messenger of Islam: His Life & Prophecy By Hajjah Amina Adil, page 292
 The Life of Muhammad, by Muḥammad Ḥusayn Haykal, page 218
 Atlas on the Prophet’s Biography, Places, Nations, Landmarks, – (Al-sīrah Al-Nabawīyah), By Dr.Shawqi Abu Khalil, page 122
 When The Moon Split, by Safi-Ur-Rahman Mubarakpuri, page 147
 The Life of Prophet Muhammad: Highlights And Lessons by Dr. Mustafa As-Sibaa’ie, page 879