Tirmidhi

1:
That is, maintain a moderate posture such that the abdomen remains level, both elbows are raised from the ground, and the sides are separated from the body, and the abdomen is also separated from the thighs.
It should appear as if there is a gap between the ground and the upper half of the body.

2:
By "like a dog" is meant that it sits by spreading both its elbows on the ground;
do not perform prostration (sujud) in this manner.

Benefits and Issues:
➊ The meaning of moderation in prostration (sujud) is that one should neither remain so high that some parts of the body required for prostration do not touch the ground, nor should one go so low that the entire arms rest on the ground, or the stomach touches the thighs. It can also mean that one should neither prolong the prostration excessively nor make it too brief. However, a very lengthy prostration is prohibited when someone is praying behind you, whether it is an obligatory (fard) prayer or a voluntary (nafl) prayer.

➋ When a dog sits on the ground at ease, it spreads its entire forearms on the ground. It is not correct to spread the arms in this manner during prostration. Rather, the palms should be placed on the ground, and the elbows should remain raised above the ground, as has been mentioned in previous ahadith.