To what extent is the prophetic prohibition against employing a worker before agreeing upon his wage authentic?

The hadith "He [the Prophet] forbade hiring a laborer until his wage is made clear to him" is weak due to an interruption in its chain of transmission. Imam Ahmad narrated it from Hammad ibn Salamah, from Hammad ibn Abi Sulayman, from Ibrahim, from Abu Sa'id al-Khudri. However, Ibrahim did not hear from Abu Sa'id. Abu Zur'ah and Al-Nasa'i preferred to consider the hadith as aوقف (وقف) on Abu Sa'id. Despite the weakness of its chain, its meaning is sound and has been acted upon by the general body of scholars and the four Madhhabs, who have agreed on the condition of knowing the wage in a hiring contract, in order to prevent disputes, by analogy with a sale.