How Businessmen Develop Trust in Allah
Question

I want to know how to develop trust in Allah when doing business.
Praise be to Allah.Putting one’s trust in Allah when striving to attain what one needs is one of the signs of a person’s faith. It is more important to put one’s trust in Allah when striving to earn a living.
Abu Hatim ibn Hibban (may Allah have mercy on him) said:
“What is required of the smart man is to continually put his trust in the One Who has guaranteed provision, because putting one’s trust in Allah is the basis of faith and is the outcome of affirming His Oneness. It is the means that leads to elimination of poverty and guarantees peace of mind. No one ever puts his trust in Allah, may He be Glorified and Exalted, with full sincerity – to the extent that for him, Allah, as He has guaranteed to support him, is more reliable than what he has in his own hand – but Allah will never let him need the help of other people, and his provision will come to him from where he did not expect.” (Rawdat Al-`Uqala’ wa Nuzhat Al-Fudala’,  p. 155)
With regard to how to develop trust in Allah when doing business , the individual must pay attention to the following:

He should believe that Allah, may He be Exalted, has already allocated provision to people, and He decreed that from eternity.

Abu Hatim ibn Hibban (may Allah have mercy on him) said:
“The smart man realises that the shares of provision have already been decided and Allah, the Most High, Who is faithful to His promise, has guaranteed that He will make it available to His slaves at the time when they need it. Striving to get what He has guaranteed is not the attitude of people of resolve, except in the case of one who believes deep in his heart that even if he does not strive for what he is seeking, his provision will come to him from where he did not expect." (Rawdat Al-`Uqala’ wa Nuzhat Al-Fudala’ p. 155)

When it comes to attaining his provision, he should cut off any relationship between him and anyone other than Allah, may He be Exalted.

Abu Hatim ibn Hibban (may Allah have mercy on him) said:
“Putting one’s trust in Allah means not relying on any created being, and showing humility to Allah, Who is able to change one’s situation.
A person may be wealthy in terms of worldly accumulation, but he puts his trust sincerely in Allah alone , so that poverty or wealth are all the same for him and he sees no difference between them, and when he is well off he is grateful and when he is poor he is content. Another man may not possess anything in this world, no matter how hard he tries, and he does not put his trust in Allah, so that becoming wealthy is dearer to him than poverty, and when he is poor he is not content with his situation and when he is well off he is not grateful for it." (Rawdat Al-`Uqala’ wa Nuzhat Al-Fudala’,  p. 156)

The heart of the one who is seeking provision should be attached to Allah, his Lord, may He be Glorified and Exalted, whilst he also takes appropriate measures and strives to earn a living.

Among the evidence that putting one’s trust in Allah also includes taking appropriate measures is the report narrated from Abu Tamim Al-Jayshani (may Allah have mercy on him), who said: I heard `Umar (may Allah be pleased with him) say: I heard the Messenger of Allah (blessings and peace of Allah be upon him) say: “If you were to put your trust in Allah as you should, you would be given provision like the birds: they go out hungry in the morning and come back with full bellies in the evening.” (Narrated by At-Tirmidhi (2344) and Ibn Majah (4164); classed as authentic by Al-Albani in Sahih At-Tirmidhi)
Ibn Kathir (may Allah have mercy on him) said:
“Taking measures to earn a living does not contradict putting one’s trust in Allah – and he quoted the Hadith, “If you were to put your trust in Allah as you should …” – This Hadith shows that the birds go out in the morning and come back in the evening to seek their provision, despite their trust in Allah, may He be Glorified and Exalted, for He is the one who creates opportunities, makes things easy and creates means and measures." (Tafsir Ibn Kathir,  8/179)
Shaykh Al-Islam Ibn Taymiyah (may Allah have mercy on him) said:
“The individual’s heart should be reliant upon Allah, not on the means or measures, and Allah will make easy for him the measures that he may take to rectify his condition in this world and the hereafter." (Majmu` Al-Fatawa,  8/528)
Shaykh `Abd Al-`Aziz ibn Baz (may Allah have mercy on him) said:
“Trust in Allah combines two things, the first of which is: reliance on Allah and believing that He is the creator of means and measures, that His decree will inevitably come to pass, and that all things are  in accordance with His decree, for He, may He be Glorified and Exalted, has written them all and nothing is omitted.
The second thing is taking appropriate measures, for failing to take measures is contrary to trust in Allah. In fact, trust in Allah combines taking appropriate measures with relying on Allah, and the one who fails to take appropriate measures has gone against both Islamic teachings and reason." (Fatwa Ash-Shaykh Ibn Baz,  4/427)
See the rest of the words of the two Shaykhs, and further details concerning this issue, in this answer: Fear of losing the means of provision and being attached to those means .

He should think positively of Allah, may He be Exalted, and turn to Him in supplication , beseeching and asking of Him.

Shaykh Al-Islam (may Allah have mercy on him) said: 
“The one who is concerned about the issue of provision should turn to Allah concerning it and call upon Him, for Allah, may He be Glorified, said, as His Prophet (blessings and peace of Allah be upon him) narrated from Him: “All of you are hungry except the one whom I feed, so seek food from Me and I will feed you, O My slaves. All of you are naked except the one whom I clothe, so ask Me to clothe you, and I will clothe you.” (Narrated by Muslim)
For a powerful discussion by Shaykh Al-Islam Ibn Taymiyah (may Allah have mercy on him), please see the following answer: What are the best fields of worldly work, employment or trade?   
And Allah knows best.