It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "When the Iqamah is called, do not come running, but come with dignity and calmness. Whatever rak‘ah you catch, perform it, and whatever you miss, complete it (afterwards). Indeed, when any of you sets out intending to pray, he is already considered to be in prayer."
Hadith Referenceالسنن المأثورة / باب ما جاء في صلاة الخوف / 68
Hadith Takhrijصحیح مسلم، المساجد ومواضع الصلاة، باب استحباب اتیان الصلاة بوقار وسکینة، رقم: 602۔