According to ISNA, President's message is as follows:
In the Name of Allah, the Most Beneficent, the Most Merciful
Your Excellency, Mr Alexander Lukashenko,
The honorable President of Belarus,
I congratulate the national day of Belarus to your Excellency, the government and the people of that country.
I am confident that ties between the Islamic Republic of Iran and the Republic of Belarus will be further developed to serve mutual interests of the two nations.
I pray to the Almighty for your Excellency's health and success, and the people of Belarus's felicity and prosperity.
Hassan Rouhani
President of the Islamic Republic of Iran