[A contractor paid money to the bank so that it would guarantee him]

The answer – and in Allah is success: What appears to me – and Allah knows best – is that it is permissible, for:
1. The basic rule in transactions is permissibility.
2. The one who pays money to the bank is paying it in return for a benefit which he obtains from the bank, so this is not consuming people’s wealth wrongfully.
3. The contracting party has stipulated upon the contractor a bank guarantee; if he brings it, otherwise he will not be given the contract. The contractor counts it as part of his potential loss in the contract, and he does not agree to the contract unless he is sure he will obtain an attractive excess (profit). Thus, what he has given to the bank is reckoned in reality upon the contracting party .

Source: Min Thimār al-ʿIlm wa al-Ḥikmah vol.2