"The widespread devastation caused by flood waters shows that it is due to our sins," Saeed said while talking to a delegation of JuD workers at the organisation's headquarters in Chauburji, Lahore.
He regretted that the country was not demonstrating the spirit of sacrifice it used to in the past.
"In the past, the whole nation would get united whenever any calamity hit Pakistan. The same spirit is required today to face this testing time...We will have to come on the path of righteousness," he said.
Nearly 1,700 people have lost their lives and over 14 million have been affected by the floods in different parts of Pakistan.
Floodwaters are still threatening some districts of Punjab, Sindh and Balochistan province.
Saeed said the devastation was much more than the statistics put out by the government.
The JuD has been at the forefront of relief efforts in some flood-affected areas under the banner of its front organisation, Falah-e-Insaniyat Foundation.
Observers have said the JuD has sought to fill the gap in relief operations due to the tardy response by the government in a bid to gain support from the people.
Saeed, also the founder of the banned Lashkar-e-Tayiba, asked his workers to devote themselves to relief efforts.
He directed them to send the maximum number of JuD volunteers to flood-hit areas.
"The government, army and NGOs cannot deal with this disaster on their own and require the support and cooperation of the whole nation," he said.
He asked his workers to ensure that all affected people were provided with food for the 'sehar' and 'iftar' meals during the holy month of Ramzan, which began on Thursday.
The Jamaat-e-Islami, which too is involved in relief efforts, called on people to ask for forgiveness from God on August 13.
"We should observe a 'Day of Forgiveness'. Such huge destruction by the floods shows that God is not happy with us. We can only deal with this flood with the help of God," Jamaat chief Syed Munawar Hasan said.
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