Anas ibn Mālik (may Allah be pleased with him) reported that the Prophet (may Allah's peace and blessings be upon him) said: “The Hellfire will keep on saying: Are there anymore (to come), until the Lord of Honor puts His Foot therein. It will then say: I had enough! I had enough! [I swear] by Your Honor, and its sides will come together and it will retreat.”
Allah, the Almighty, tells that He asks the Hellfire: “Have you been filled?” because He promised that He will fill it with both Jinn and Humans. Allah, the Amighty, will summon whom He wills to enter Hell. As they are thrown therein, the Hellfire will ask Allah for more. Hence, Allah will put His foot in it, so the Hellfire will say that it has received enough and will contract. It is not permissible to interpret “foot” here to mean those people whom Allah put in the Hellfire. No other invalid interpretation is allowed. It is, however, mandatory to affirm the “foot” as an attribute of Allah, the Almighty, without altering its meaning, denying it, asking how, or drawing similarities.