What is the meaning of tathbīt in this āyah?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. It refers to spending out of certainty and conviction. [al-Shaʿbī, Qatādah, al-Suddī]
2. It refers to careful consideration of where to spend, meaning they deliberate on where to place their charity. [al-Ḥasan, Mujāhid, Abū Ṣāliḥ]