In Q1 Hamilton was seen moving off the track through a wet Eau Rouge - Raidillon complex on driver's left and rejoined the track directly ahead of team-mate George Russell, when both Mercedes drivers were on their out laps.
Russell had to take avoiding action, while behind them the Alfa Romeo of Valtteri Bottas was also hindered.
The incident was reported to the stewards, who investigated it after the qualifying session when both Hamilton and Russell were summoned.
Hamilton argued he simply wanted to jump out of the way of Bottas, who had just started a flying lap.
Russell also explained he wanted to make sure Bottas wasn't impeded, and thought there was no danger to the way Hamilton rejoined the racing surface atop Raidillion.
The stewards followed their reasoning and decided to take no further action.
"Hamilton explained that he had been warned of the approach of Bottas and moved out of the way, in this case off track," they wrote in their verdict.
Source: Autosport